S TIER
XBOX: This was by far the cheapest, easiest, and one of the most fun consoles to collect for. I don't think I ever spent more than $10 on any XBOX game, even really rare, expensive games like JP Operation Genesis. It was also the first console I stopped collecting for because I felt like I had every game I wanted for it.
PS2: Another 6th gen console. This was another extremely fun, cheap console to collect for when I was actively picking games up for it. The peak of my PS2 collecting phase coincided with everyone not caring about the PS2 thanks to the PS3 being towards the end of its life, and the PS4 being around the corner. In other words, the games were everywhere and generally cheap as hell. I did have to pay full price for a few of the games for it, but 90% of my PS2 library was obtained for $10 or less. The PS2 was also the console I had the most games for at one point, somewhere near 350 if memory serves me right.
Gamecube: Like the XBOX and PS2, this was also an insanely easy, cheap, and fun console to collect for. I'm not a huge Gamecube guy, but when I was out looking for retro games at flea markets and thrift stores, these games were everywhere. I'd find rare game after rare game for a few dollars each, and at one point had a GC collection that would have made modern GC collectors eyes explode. I even found Gotcha Force for like $10 at the flea market. There were a handful of GC games I paid full price for, but in general this was a console that was in plentiful supply between 2008 and 2014 or so when I obtained 95% of my GC collection.
N64: Despite collecting for the N64 nearly a decade after Nintendo pulled the plug on it, I never had much trouble collecting N64 games back in the late 2000s and early 2010s. Similar situation to the PS2 and XBOX; the games were everywhere and generally very cheap. I did run into some trouble with a few games I wanted towards the later part of the 2010s, but overall this was a very fun, easy console to collect for when I was actively pursing a big chunk of its library. It also being my favorite Nintendo console also helped.
A TIER
PS1: I probably obtained 80% or so of my PS1 library on the cheap, including a lot of super expensive and rare games. The PS1 also has an incredibly interesting library of games with hundreds of games that had my interest when I was actively looking for games on it. The only reason the PS1 isn't S TIER is because I had a hell of a time finding certain games for a good price, and several games I just couldn't find at all. I also paid full price for a decent chunk of the PS1 games I'd eventually own. Otherwise though, it was one of my favorite consoles to collect for, and also to game on.
Dreamcast: Being my favorite console of all time, you'd think this would be S-TEIR, but unfortunately due to how hard it is to find Dreamcast games, not even including the rare ones, it took me a very long time to get all the games I really wanted on it. I'd say roughly half the games I've owned on the Dreamcast were found very cheaply at garage sales, flea markets, and second hand stores, but nearly just as many I paid full price for online or at game stores. Still, I cherish the games on it, and never felt guilty for picking any of the games up at whatever price I found them at.
DS: This was another instance of the games being plentiful and cheap. I found nearly all of my DS games for way under their respective prices at the time I found them. The only thing that keeps this one from being S Tier is I'm not a huge handheld fan (although the DS is my favorite handheld console of all time) and because some of the games I bought from places like Gamestop brand new when they came out, which does take a little bit of the fun away.
B TIER
SNES: I found a decent chunk of my SNES games for pretty cheap, however I had a much harder time finding a lot of the games I wanted for a decent price since the NES and SNES were the two retro consoles to get hit the hardest by collectors (and resellers) early on when I began collecting. Still, I got some insane deals on various games over the years. If not for the difficulty of finding many of the games I really wanted on the console and also if I was a slightly bigger fan of the console, this one may have ranked a higher.
Genesis: Similar story to the SNES, however I admittedly had better luck finding cheap Genesis games than I did the SNES. Despite being a Sega kid in the 90s, I for some reason didn't enjoy collecting Genesis games as much I felt I should. No matter though, I still had a blast with it for the most part, and found some crazy deals on some of the Genesis' most sought after games.
Saturn: If I was less of a Saturn fan, my experience with collecting for it would have been C Tier tops, maybe even D Tier. Aside from a few surprise scores, Saturn games have always hit my wallet and patience hard. I also have spent a lot of time and money collecting various Saturn imports that we never got in the US (Or just cheaper import alternatives). But with the Saturn being one of my favorite consoles and also one of my most nostalgic consoles, nearly every time I added Saturn games to my collecting I'd be overjoyed. I just wish my experience with getting the games had been a bit easier...and cheaper.
Wii: My Wii collecting coincided with the Wii's twilight years, and while the games were for the most part not bargain bin priced, they were everywhere and the occasional deal could be found. While I loved the Wii when it first came out, collecting for it made me appreciate it even more, making my journey to find the games on my want list for it that much more fun. The only thing that holds my experience with collecting for the Wii back is that most of the games I bought were found at Gamestop and various video games stores I visited over the years.
PS3: Similar situation to the Wii. I bought the bulk of my PS3 games on sale or semi on the cheap when the console was still Sony's current gen platform. I also paid full price for a decent amount of PS3 games when they were first released. Still, I am a big PS3 fan, and was even more so back in the early 2010s. By the time PS3 games started becoming less desirable and probably significantly cheaper, I had already acquired 95% of all the PS3 games I'd ever wanted.
C TIER
PS4: I've essentially bought all my PS4 games as new releases since the console came out in 2013, or through various B2G1 or B2G2 sales at Gamestop and other game stores. I love the PS4, actually more than the PS3 now, however my collecting experience has more or less been fairly uninteresting compared to when I was scooping up PS2 or XBOX games for a few bucks each all over the place. There's also the big question mark about the longevity of these games and people's ability to continue to play them after their respective servers get shut down someday.
WiiU: Same situation as the PS4. I bought 95% of my Wii U games when Nintendo was still supporting it, before they released the Switch. I was a heavy supporter of Nintendo's ill fated console, however the lack of games and the consoles short life definitely dampened my experience of collecting for it. And again, just walking into a Gamestop and buying a WiiU game off the shelf lacks the thrill of finding some rare old game at a flea market or thrift store.
3DS: I'm going to sound like a broken record, but this was the same situation as the previous two C Tier consoles. Nearly all my 3DS games were purchased while the handheld was still being supported by new, big releases, and many of those games were purchased at various retail stores both new and used. And while I do have a massive soft spot for the 3DS and have enjoyed some excellent games on it, my lack of enthusiasm for handheld systems in general made this a less enjoyable console for me to collect for.
GBA: I've been very fortunate to have found so many GBA games I have for so cheap, but again, me not being a big handheld guy made collecting for it somewhat lackluster despite scoring some incredible deals on some of its rarer and best games over the years. I still have a ton of GBA games in large storage cases that I go through from time to time, but over the years I have not been able to bring myself to part with many of them.
PSP: Apply everything I said about the GBA to this handheld too with the exception being that my PSP collection is about a fourth the size of what it once was at its peak. I picked up the overwhelming majority of my PSP games for under $10.
Switch: I've continually bought Switch games since it came out in 2017, but nearly every game I have for it has been from retail, mostly new. I love the Switch and some of the best games I've ever played are on it, but from a collecting standpoint, there's been nothing interesting or exciting about it for me.
D Tier
NES: I found out very early as a collector that I was far less into the NES that I originally thought I was. That didn't stop me from acquiring a fairly large collection of many of its must have games, with a few rarities thrown in here and there. In fact, I think my NES collection nearly hit 100 games at one point. Yet, despite finding some pretty sought after games for just a few bucks in the wild, I never got too excited about adding new NES games outside a handful of titles. It was one of the first consoles I ever did a massive downsizing with, and to this day I still don't regret parting with any of the NES games I once had. Collecting for it when everyone was feverishly collecting for classic Nintendo back in 2010 and 2011 didn't help matters either, although I still did pretty good if I say so myself.
360: There was a time where the 360 was my goto console over the PS3, however, the PS3 would eventually win me over way more, leaving my pursuit of 360 games limited only to console exclusives that interested me. I was able to find most of these easily and cheaply enough, but the 360 just never really did it for me like the original XBOX, and in many ways its the last Microsoft console that actually appealed to me at all. Overall though, it was a fairly boring and uneventful experience of collecting for it, and I've acquired every game I've ever wanted for it years ago.
Gameboy/GBC: For however much I'm not a big handheld collector, I'm especially not a big Gameboy guy. Gameboy to me is essentially Pokemon, Tetris, Mario, Zelda, and very, very few other games. I found almost all these for dirt cheap a long, long time ago, and aside from a few exciting moments and scores, it's just not a platform I'm that into.
Neo Geo Pocket: I only include this in D Tier because the collection I had of about a dozen loose games for this handheld were found at the same time, all for extremely cheap. The score was very exciting to me at the time, but outside this I never found any of the games for the system, and worse than that, I never ever owned an actual NGPC handheld to play them on. By the time most of the system's best games were ported to the Switch, I decided to part with the original games and have never looked back.
Sega CD: I really wanted to get into Sega CD collecting, and at one point I think I had maybe 10 games or so on it. But with no hyperbole, I'd say all but maybe a few games I had for it were absolute garbage or at least mediocre. What made matters worse is the supposedly better games on it were insanely expensive and even the ones that weren't were nowhere to be found most of the time. I gave up on Sega CD collecting a long time ago, and have never looked back.
PS5: I struggle to even call myself a PS5 collector since I know full well its physical games are more or less glorified CD keys. I don't think there is any future in collecting for the PS5 since I know these games will have no longevity in a decade or so from now when Sony pulls the plug on its servers. Nearly every PS5 game I've played requires at least half the game be downloaded, if not way, way more than that. And I've never been able to have more than a dozen or so games downloaded onto my PS5 at a time given how much space they take up and also there being no way to update the HDD in them. If not for the games being petty fun, this would be a straight up F Tier console in terms of collecting for me.
F TIER
XBONE: I own a few XBONE exclusives despite not actually owning an XBONE console. Sometimes I wonder why I even have the games I do. I will pick up an XBONE, but only when one can be had for $50 or less. That's literally my top dollar on the system. There a maybe a few more games I want to own for the XBONE, but in all, I doubt I'll ever break 12 games on it.
TG16/PCE: I really like the PCE, however outside a handful of games, I've never been able to find anything for it, much less the console itself. Sure, various retro game stores I've been to over the years have had them, but they've always been way overpriced, and if I'm being completely honest, I don't actually know much about the system in general. I recently opted to get a PCE console along with a Super SD Pro to play the games on given how insanely hard and expensive it is to find the better games for this console.
Neo Geo AES: I have never been able to justify AES collecting despite being a massive SNK fan. Paying $300 for a game like Metal Slug or King of Fighters has always been too big a pill to swallow for me, especially with so many modern alternatives. Still, I have a Japanese AES and a few games for it. Someday I plan on getting a Neo SD for it just so I can play the entire library of games on the original hardware, but until then I'm happy with the various ports of the AES's best games or even emulation.