I never really played anything but chess in my phone (call me a freak if you want) but i can list 2 games that i frequently play.
1. Carmageddon (Part 1!, AWESOME!)
2. John GBC Emulator (as the name suggest, it's a GameBoy Color Emulator)
That pretty much sums it.
I've been willing to play Doom on my phone, do you know if it's possible?