My first Game Boy was that original big gray one with the green screen (I kept telling myself it was black and white, but my eyes knew it was green. Made lava levels interesting anyhow). I had the usual pack-in carts: Super Mario Land, Tetris, Home Alone, and whatever else it came with. Dumped Home Alone like a lead balloon after I had to struggle to pass the first stage. Tetris, obviously, got a lot of play although I preferred the NES version for its colors and music (I'm one of those people that liked the NES's Type C music which hasn't appeared in any Tetris game since). Super Mario Land I hated, thought it was unfair and too hard. So it amazed me when I saw a friend beat the whole game in front of me. Eventually I was able to do the same (in between the silent cursing).
So the original Game Boy was good. Got a Game Boy Pocket when it came out, was initially wowed by how it was easier on the eyes (I think it made Donkey Kong '94 slightly easier too)... but little did I know it would be the most worthless purchase in my life. It wasn't too much later that the Game Boy Color came out and I had to have that. Seeing as how certain later Game Boy games were incompatible with the early ones, I had to make the change. Then I had to have the Game Boy Advance, although I got sticker shock from how expensive it was, to me it seemed as expensive as a GameCube. At that time I realized I didn't play handheld games much anymore (I just preferred the games with more substance, and I was usulaly at home), so I just stopped buying them.
That said, I still have four Game Boy games lying around. Donkey Kong '94 (even though I cleared the entire game except the last stage in a marathon playthrough), Hexcite (I'm bad at strategy, so the game keeps me on my toes although I always have trouble beating the CPU), Game & Watch Gallery 2 (keeping that one primarily because I took a liking to "Parachute"), and Wario Land 1 (I just prefer the environments and general goofiness of that one, even though the later games had superior level design. I guess I still have a soft spot for Jet Wario and Dragon Wario).
And the two games I remember losing were Super Mario Land 2 and Wario Land 2. Hey, if it fell under a car seat, it was as good as gone.