To answer your question, I guess anything for the Sega. I was 100% a Nintendo kid when I was growing up. The school sold magazines as a fundraiser and the only gaming mag was Nintendo Power...I was completely oblivious to what was out for the Sega. Also, my parents were pretty overprotective and they bought into the hype when Mortal Kombat came out and the Sega version had blood and spine-pulling and all of that.
So I was in college, in 2002 or so, when I played the original Sonic the Hedgehog for the first time (besides demoing in a store). By this time I owned Sonic games (Sonic Adventure 2 Battle was one of the first 3 games I got for my Gamecube -- other two were Smash Bros. Melee and Pikmin) and I knew the characters. But I had never played a game on the Genesis until then (besides Lion King and Aladdin...a friend had those).
My college roommate my Sophomore year took me under her wing and got me up to speed on the Sega world, however. She had been a Sega kid all the way through the Dreamcast, and she made sure I could hold my own on Sonic, Ecco, Shining Force, Soul Calibur, Skies of Arcadia, Jet Set Radio, and Space Channel 5, among others.
Some of my favorite games are now Sega properties, and some of the best new experiences I've had with retro games have been for the Genesis. Ronalopolis was sorta a Sega kid so that helps as well, and I've had to admit that sometimes Sega games were pretty good too.