I think by now my thoughts might already be known. I honestly kinda hate the Game Boy. I think it's a woefully bad system. I remember trying to play it, and having to pitch the screen in a certain direction towards the light just see it. Half the time the graphics were so lame and shrunk down you could barely tell what you were looking at. Nintendo didn't take portable gaming seriously back then, it was just a novelty. It was seen as a toy that kept kids quiet. Hence the name, Game Boy. It even sounds like a child's toy. It doesn't matter what titles it has, they were all abominations to play on Game Boy. You have to have the Game Boy player for TV, otherwise forget it.
Game Gear I never knew about until much later, and I felt cheated. I didn't play one until I got into game collecting, and even then I was very impressed with what it could do for an early 90s handheld. The games look great, IMO. Basically every other handheld I've researched or come across since has been infinitely more appealing than the Game Boy was. All of the competition should have stomped the GB, but the cheap price tag and tiny form factor of the Game Boy made it parent's number one choice for their kid... kind of like the Tiger handheld games.
Sure, the GG eats through batteries, but rechargeable batteries exist for a reason. There were also third party rechargeable packs you could buy for GG. Yeah, it makes it more bulky, but I don't see what the issue is with people's perception of size and handheld systems. Like, I don't want a handheld to be tiny anyways. I don't want to put a handheld system literally into my pocket. Nobody does that nowadays, nobody complains they can't fit their 3DS XL into their pocket and nor should they be trying to. You need to a get a proper travel case for it whether it's a Game Boy, or a Switch. Size in not an issue, and bigger screen is better. Color screen is better. Lit up screen is better. Graphical power is better, lol. All of which Nintendo has finally embraced in their approach to handhelds thankfully.
Nowadays, I don't play a lot of old-school handhelds, but when I get the craving to do so it's usually Game Gear. Which is a platform I still collect for, although not actively at the moment. I'm actually somewhat intrigued by the Lynx as well as the Neo Geo Pocket Color... and may consider starting collections for those at some point. Game Boy on the other hand, I don't collect for. Probably never will.