Good Sci-Fi shooter, but online multiplayer needs a lot of work .
*** UPDATE 6/11/06 ***
After playing approx. 500 multiplayer ranked matches, I've grown weary of waiting for game matches to begin; 90-120 seconds is a long time to wait over and over and over for every match to begin, and very often connections will hang or lag upon entry. In addition, server connection quality and dependability vary wildly, creating issues where controller sensitivity is often too high or too low, game lag to the point where you have to restart the game (yet another 90-120 sec. wait), and other things like failed connections and Xbox Alert errors (again, with another 90-120 sec. wait). Generally, I feel as though more time is spent trying to find good connections than enjoying the game. Load and wait times were the sole reason I sold my PSP (that, plus the fact that the game controller config. sucks). I have never experienced any of the same issues with other Xbox multiplayer games.
Lastly, I rather detest the fact that you can't simply host a game and select a specific map to use like you can with Doom III; maps in multiplayer ranked matches are only randomized in Quake 4. The game feels rushed. It could have been much better; it could have been special. Xbox 360 needs more Sci-Fi FPS shooters. I loathe the perpetual barrage of miltary-based themes like GRAW, Outpost, Battlefield 2, Far Cry, Ghost Recon, etc. It's obvious they're holding out on the Sci-Fi FPS games in order to generate extreme anticipation for the big Halo 3 release. I'd like to see more online multiplayer releases in the likes of Gun, Dark Watch, Area 51, Mech Assault, etc.
Doom III is arguably the best online multiplayer FPS game next to Halo 2, but those were made for original Xbox, and it doesn't look like Microsoft will make Doom III playable on the 360 any time soon.
Quake 4 is a decent campaign game, and multiplayer is reasonable if you pick a day when connections are good (like Wednesdays).