The Game Gear was outrageous for it's time... with it's only set back being it's battery life of 3-5 hours per 6 AAs. Imagine if the Game Gear was re-released today with modern tech instead of those Micro things.
Well.. For me Game Boy Advance was Game Gear 2.
Long lasting lithium battery,
with port/likeliness of Dreamcast games (instead of Master System & Mega Drive) :
Crazy Taxi, Chuchu Rocket, Sonic Battle, Space Channel 5, and Jet Set Radio.
Not to mention Super Monkey Ball Jr, Shining Force, Gunstar Super Heroes, and Sonic Advance Trilogy.