As long as we're talking backwards-compatibility, would you entertain Gamecube suggestions? (I suppose you can see a bias in my recommendations)

If so, I can't recommend highly enough the following two games. They sold horribly as Gamecube exclusives, which is a shame, because they're some of the best games I've ever played period:

Eternal Darkness
Beyond Good and Evil

Those games are simply brilliant. Beyond Good and Evil is one of the extremely rare games that makes you care about the characters, and the gameplay is terrific. Eternal Darkness, on the other hand, will have you freaking out. It is to only be played in a dark room. Both of these games still hold up (they're only one generation old), and I play them regularly.

Beyond that, I've heard good things about Resident Evil 4 for the Wii. The Wiimote controls apparently make what was considered a great game even better.