I hope this doesn't turn into another "just list your favourite games" thread. It's interesting to talk about how games would actually work on a touchscreen. Outrun is an obvious choice, we've got enough racers to show us that could work well.
I would be interested to see if SEGA could create a precise and reliable swipe-controlled system for a Shinobi game. I can imagine using fast, directional swipes to bound off walls and the heads of my enemies.
Oh, and in a similar vein to Outrun, I'd love to see Road Rash make a worthy return, but I think that still belongs to EA, and they're being a bit annoying as of late...