This game is one of the masterpieces in todays gaming world. It has great multiplayer and impressive single player.
To start I'll write something about it's single player. It's not like Half- life or F.E.A.R., UT 2004 doesn' t have story like that games, you don't have levels to pass and weapons you are getting as you are passing through the game. UT's single player is more like Quake 3 Arena. You have one map to pass (it can be Assault, Death Match, Capture the Flag, Bombing Run, Onslaught...) and after wining it you unlock next map.
One of the best things in Unreal Tournament 2004 is the return of the Assault mod ( originally from first UT ), which was not seen in UT 2003.
One of the new mods is Onslaught. In that mode you have to conqer bases (Power Nodes) and connect (link) them so you can finish game with destroying enemy's base (Power Node).
Also there are other mods which we've seen in UT 2003 and original UT, they are: Death Match, Team Death Match, Bombing Run, Capture The Flag, Invasion, Mutant, Onslaught, Assault, Vehicle Capture The Flag.
Second is Multi Player. I personally like it more because it's more exciting and more fun. All mods available in Single Player is also available to play in Multi Player. You can play it on LAN or Internet. Maps that are most played on Internet (on Death match mod) are Rankin and Deck 17. Those are also my favourite maps.
One last word: All of you who haven' t played this game yet you must try it, it's amazing and even if you don't like this genre (fps), you'll surely love it.