After a kind of dreadful first hour or so, it picks up and becomes a halfway decent shooter. Still the worst Quake campaign, but not a total trash fire.
The Xbox 360 port is one of the biggest technical messes I've played, I'm not one to dog on Frames per second but this was flat-out unplayable at many parts. Other than that when it worked it was okay, not remarkable but okay.
Pretty much a faster Doom 3. I still prefer Doom 3 though because the Hell levels are just the perfect interpretation of Hell I've seen in a game, and Quake 4 almost has this Halo element to it in terms of aesthetics, but with body horror. That body horror though is pretty nasty, especially with the lower-tech low poly models. The vehicle sections are pretty awful, but the core shooting can be fun with awesome sound design. I just wish one day, we get the dark fantasy version of Quake back in a future installment, rather the Strogg again.
Other than that when it worked it was okay, not remarkable but okay.