Quake 4 didn't try anything fancy. It did what it set out to do, and that's what counts.
So, what does Quake 4 have to offer? Nothing but a brutal, fast-paced, no holds barred, adrenaline-pumping, shoot-em-up festival that will keep you on your toes and your eyeballs popped from beginning to end. Done to death? Yes. Any new strides this time around? Nothing worth mentioning. All that counts is that Quake 4 is extremely intense and a BUTTLOAD of fun. A hell of a rollercoaster from beginning to end. Even though it's not very long, I wouldn't mind if it took 50 hours to finish it up.
Behind the insanely good looks is the very heart and soul of FPS in it's purest, simplest, and most unadulterated form. Games like this are very rare, and downright underestimated.