Some Halo 2, here a bit of Doom3 and there some Quake 2,too and everywhere
As the title says Quake 4 is more like a mixture of Halo 2 and it's vehicle levels plus Doom3 with just 5 times more monsters. You only need to kill as much monsters, zombies war machines as possible, sometimes you can use some of those marines, which will follow you sometimes to help you, like healing, repairing armor or kill as much monsters... The level design will force you to go always into the right direction, that's more boring then helping .
Graphics:
The Doom3 engine in action. Not that dark like Doom3, bigger levels bigger hall ways, more places outside and a lot of different vehicles, like a tank a mech or even a tram rail way and many more. And the textures are this time much sharper and detailed then in D3 as well as the bump mapping. But this has got also a bad side of the coin: Because it's not so dark the specular mapping will be messed sometimes, also the polycount is sometimes "strange". You can not judge if those character models have enough polys or not.
Design: Yeah that's Doom3 and Quake design, too bad that there are not enough more organic inspired level design instead of "blocky" "brick" builded "Lego houses"
Sound: from a technical stand point, wow, EAX 4.0 that's awsome, excellent 3D sound effects, from all the other stand points, it's more boring and sometimes you even hear no music because those guns are to load, but all in all it depends on taste of the gamer
Value
ALL IN ALL:Technically a great game, not a masterpiece, just great... But gameplay is too short, "fast food killing", old school Quake combined with some new ideas like those marine support system and those vehicle levels