new 360. what games should i get?

I just ordered an Xbox360 from ebay. My brother only wants a 360 for NHL 08 and 09 (and the other NHL games). I'm not so dumb. The three games I really want right now are Halo 3 (I'm a huge Halo fan, and I own both 1 and 2), Assassin's Creed (I've played it at a friends, and its really fun), and Call of Duty 4 (just plain fun).

Are those good games to buy right now? What do you think is the best game on the 360? Help please!

CoD4, Gears Of War, GTA4 are all awesome

I wouldnt get bioshock or assassins creed because niether have any replayabilty there rentals in my opinion