OK, these are my Top 20 Game Gear games:
Bust-A-Move
Columns
Castle of Illusion Starring Mickey Mouse
Deep Duck Trouble
Gunstar Heroes (Import)
Joe Montana Football
Land of Illusion
Legend of Illusion
Mighty Morphin' Power Rangers
NBA Jam
Sonic Blast
Sonic Chaos
Sonic Drift 2
Sonic the Hedgehog
Sonic Triple Trouble
Streets of Rage 2
Tails' Adventure
Tempo Jr.
The Lucky Dime Caper
I love the Game Gear to death, but boy does it have a shitty library. At least there are some really good ports and some great SEGA games on it.