Go to your local Target, and check to see if they have a $14 gold kit.
I'd pick up Burnout (it's fun as hell), CoD2, and Kameo. They can be had for reasonably cheap, and are a good start without plunking down the same for a single game. Don't forget Live Arcade though.. get Geometry Wars, Worms, Alien Hominid, that damned Marble game, and Castlevania whenever it comes out. All of that should keep you occupied for a good while, and not kill your wallet as much as new releases.
I personally liked Battlestations Midway, and get a kick out of the multiplayer. It isn't as realistic as I'd prefer (the aircraft don't even have altimeters and the guns have unlimited ammo), but I enjoyed the mass strategy aspect of gameplay with naval warfare (the first console game I have EVER seen that actually acknowledges the fact that a shell can ignite a ship's gun magazine and blow it up). I hope they support the online portion a good bit (add
B-29's!!).. but it's a love it or hate it kinda game.
Honestly.. I'd stick with what is established as good and get the cheap stuff first. Hell, Burnout alone will keep you occupied for hours. If you want to splurge, Oblivion will suck away your life... you'll get your money's worth out of it.