Sonic the Hedgehog for the Genesis. I was only 5 or 6 at the time but that opened up a whole new world for me. It was one of the first video games I ever played, along with Mortal Kombat. I actually learned how to play the games, but I also knew the cheats, tips, secrets, and shortcuts. I would cry because I could never get past the water level and the rising water jingle scared me. It still does to that day. My mom could get to the space level and Dr. Eggman would kill her, so I'd cry some more.
good times.