I grew up on the Genesis (I got one for my sixth birthday and played it for six years straight before I got my hands on the N64), so I mostly lived on those games for a while.
Naturally, there was Sonic, but there were a zillion other great games, many of which went unnoticed; Gunstar Heroes, Mortal Kombat, Quackshot, Rocket Knight Adventures, Virtual Pinball, Vectorman, Herzog Zwei, and so on.
I still play retro games. I bought a SNES last year and am still collecting games for it. Need Secret of Mana, Tetris Attack, and Mario Kart and I'm good. I also buy classic arcade machines, especially since they go for almost nothing. I bought a Tetris last year at a local auction for $75; while I've since then had to resell it to pay off car debt, it was an excellent piece and a lot of fun to toy with.