I heartily 2nd the ratchet and clank games. Loads of fun and safe for a 7 year old. There is an almost fanatic following for Dance Dance Revolution and you and your family might enjoy stomping on one of those. I would also recommend SSX, SSX Tricky, and SSX 3. All 3 are snowboarding games and a good bit of fun. The tony hawk skate boarding games all got great reviews. You might also consider something like Gauntlet that will let up to 4 people play cooperatively.
More mature games: SOCOM. Syphon Filter. Metal Gear Solid II. Resident Evil (series). Splinter Cell and Splinter Cell Pandora Tomorrow where two AMAZING games.
I'm not much into the sports games or the GTA style much myself so I'll leave those sorts of recommendations to others. You might also want to check out Gamefly.com (in addition to blockbuster).
I very higly recommend setting things up to take advantage of your HT. Resident Evil in 5.1 with the lights off is wet your pants creepy.
jr
