Just bought a Genesis (was always a Nintendo man), for $15. Between local game shops and Listia (auction site where you bid with points not cash), I've picked up:
Hardball! Joe Montana II Super Monaco GP Tommy Lasorda Baseball Jack Nicklaus Golf Sonic & Knuckles Mike Ditka Power Football Tinhead The Lion King Tony La Russa Baseball Coach K College Basketball Bill Walsh College Football Jurassic Park: Rampage Edition John Madden Football 92 College Football's National Championship Madden 95 College Football USA '97 NBA Jam Tournament Edition Sonic The Hedgehog (not for resale) NFL Football '94 Starring Joe Montana Sonic 2 Mortal Kombat
Lot of sports games, but they're super cheap, often a buck apiece or cheaper. Several I also won on Listia.