Atari 2600 games would be almost perfect. Think of it, the Atari 2600 had two types of main controllers:
1) Arcade Stick - 8 way directional joystick with 1 button = iPod Click wheel...touch the part of the wheel to go in that direction, hit the middle button to use the 1 button, or maybe press on one of the click wheel's sides.
2) Paddle Controller - A round circle that you can turn left and right for games like Breakout, Warlords, or Circus Atari, and there was a button on the side to press, thus again using the iPod's middle button or when force is used on one of the click wheel's 'button sides'
These games should run fine I would guess on any of the color iPods (past or present or future) - The Atari 2600 games are simple, fun, don't require a lot of speed, and you can control it without an external device. Bluetooth play would just plain kick ass
I just hope Apple reads this forum once and a while. Hell if they sold like 20 or so Atari 2600 games for the iPod for like $9 or $15 or something, hell I'd buy it. 50 cents a game? Eh? I don't think this would turn the iPod into a 'gaming console' because it would be completely be blow out of the sky by today's modern handhelds. Well unless Apple changed the iPod dramatically, which I personally don't see happening anytime in the near future. But I sure do like the sound of those Atari 2600 games...maybe that would be my sole reason to upgrade...other than my 5gb 1st gen iPod being 'special'

Damn FireWire port is going I think.

Maybe It's just because I'm a retro Atari 2600 fan