If it's not an Xbox 360 Elite (newer, more expensive) it won't have HDMI. My Xbox has a USB connector just above the Ethernet jack. It's primary purpose is for connecting the Xbox Wifi adapter, which mounts on the back of the console. Older Xboxes use component input for HD, which works fine (mine gets 1080p).
Actually, that's not true. The Pro version was updated last summer with HDMI. Omnis (or whoever you actually are - I think I shall call you Faux-Omnis), if you bought your box before last summer then it's probably not HDMI.
IOXboxN; I've played very little of Halo recently. I played Halo 2 pretty consistently for 3 years and the game-play aspects that niggled me (primarily the over-powered punch and the general stupidity of a game that promotes bouncing everywhere instead of running) were not lessened but actually magnified by Halo 3. This all means I'm pretty damn tired of the game.
I am eager for Gears of War 2 because the campaign looks spectacular and the multiplayer not only has dealt with a few things I hated (shotgun charging) by adding stopping power to weapons, they've also added a 5-player "co-op" where it's the players against an endless horde of Locust. Sounds like a blast.
Anyway, for now, I'm actually playing Team Fortress 2 (found in the Orange Box package) and it's just damn fun. It has a more cartoonish style, 9 different classes you can play (scout, soldier, spy, demoman, medic, sniper, engineer, heavy & pyro) and while that variety may seem overwhelming, it means you can find the handful of classes that suit your play style and stick with them. You can also switch characters every time you spawn.
BUT, the biggest draw for me currently about Team Fortress 2 is that because the game is always Team v Team and the game hinges on cooperation, the people playing it are almost never abusive or confrontational. I played TF2 for an evening without meeting a single asshat, then played a couple of games of Halo 3 and ran screaming back to TF2. Halo just seems to attract some really aggressive racist misogynist mouth-breathers I'm afraid.
Anyway, those of you with the Xbox Orange Box, howabout meeting me sometime to try out TF2?