I was a Game Gear kid back in the day, that system did have a lot of good games but most of them were pretty obscure, I guess. Most of the SEGA ports were pretty cool. Didn't get a Gameboy until much later and stocked up on lots of titles. My cousin and I would just go to the game store, look through the box of used Gameboy games which were dirt-cheap, and buy two copies anything that had multiplayer support and looked cool. Ah, so many days just playing RC Pro-Am against each other! I had a lot of Gameboy games which names I no longer remember, but were pretty fun!
Wario Land 2 was a really cool game.
The Crystalis port for GBC sucked, such a bloody disappointment considering how amazing the NES game was.