If you like roleplaying games then Final Fantasy XI, Elder Scrolls: Oblivion or Nintey Nine Nights will be a lot of fun to play.
If you like racing games then Moto GP 3 or, like you said, Test Drive: Unlimited will be good. I'm looking forward to Moto GP 3 myself.
Rockstar Games' Ping Pong title is at the top of my wish list and it should arrive sometimes in May.
As for titles in the long future, I'm really excited about Viva Pinata, Too Human, B.C. (if it ever comes out!), Alan Wake, Stuntman 2, Crysis and Forza Motorsports 2.
You also shouldn't forget about Live Arcade -- we will have coin-op games we all played back in the old times at the arcades in the 1990's. 4-player co-op Gauntlet 2 anyone??? Complete arcade games downloaded only for a few credits?? Just plain kick ass if you ask me.