Pretty much all neo geo games can be found on other consoles with very few exceptions, not to mention most of them ports being arcade perfect.
Neo geo aes and mvs might be the real things but nowadays It's just an collectors piece especially considering the combination of the prices and pretty much all them games being easily available on other original consoles compared to other systems if were negating emulators.
Well, true enough, but considering that the OP is asking about collecting for these oddball systems, and that we're on a site called VGCollect, I figure the ports to other systems aren't a factor. Plus considering that most ports weren't close to perfect until the Dreamcast and Playstation 2 era, it really says a lot about the raw power the Neo Geo had. That's one of its big allures, an obscure system that outpowered all of its contemporaries, and was supported by a good lineup of games. It's amazing that Garou Mark of the Wolves came out on a system from 1990.
With this system you don't go on a crazy binge and buy a ton of games at once for it. You hunt for months to find good prices, and over the years you'll savor each new game you find.
Very true luckily most ports if not all wich were on the previous consoles are on the dreamcast, and ps2 even allot of obsecure ones if your also taking japanese ps2 in consideration.
Back on topic
I would avoid retro gaming stores and go on ebay, I´m pretty sure ebay has lower prices than retro gaming stores at least If I look in my own country difference can be huge since stores can charge allot more than true market value to keep their lights on.
Colecovision and vectrex games are reasonable but for the fun systems you need deep pockets, because the supply is limited deals are pretty much non existent since pretty much no one has them.
If you do have deep pockets you can hunt down games for the fm towns, the capcom home console the grafx68000 and all that kind of fun stuff but again without ebay pretty much impossible to hunt for, forums usually are not the place to hunt for certain things since the market is allot less active for these more obsecure things.
Deep pockets and ebay would be my advice.
Zx spectrum is superbly cheap even cib, Would still recommend ebay to hunt for those and to buy more at ones to save shipping costs and obviously the very slim offers that gamestores have for this console.
Gameplay wise if your really into pre nes gaming for them cheaper consoles It´s great. if not they are just collectors pieces, for most them games are a bit less to be desired.