The graphics in Aliens vs. Predator are very good, though not groundbreaking. Real-time lighting is in full effect. Smoke and water look good, though not realistic. The physics engine works well with body parts flying every which way. Alien areas have a tremendous H.R. Geiger feel to them, just like the aliens themselves. That is not surprising considering Geiger designed the original dark alien concept. Everywhere else tends to have a dark future feel, just like the Alien films. That's one problem with the graphics, everything is just too darn dark! Because of this, you spend far too much time in the lower fidelity infrared and special vision modes. On a lot of levels, you just can't play otherwise. One good thing about the darkness is that it adds a lot to game atmosphere. You almost always have that 'all alone in the dark with big scary monsters who want to eat your brain' feeling.
Character modeling in Aliens versus Predator is superb. The Alien and Predator models are just great! They're much more complicated than the FPS norm. Animation is lifelike and evil. Marine models are also quite good, though not as impressive. Since the character models are what you pay most attention to, it is good they spent so much time on this aspect.
The cut scenes of Aliens versus Predator are also quite impressive. It's your standard ray traced cut scenes, but Rebellion managed to give them a nice extra cinematic feel that is often absent in other games.
The sound effects of AvP are just perfect. The Predators make their dangerous glottal clicking sounds. The Aliens sound like a pile of scorpions being crunched underfoot, by you, when you're barefoot. And the Marines sound like the frightened weaklings they are. We can't help but be reminded of Bob from the Bungie's Marathon series. On top of all this is perfect use of 3D effects. You will learn to rely on your hearing as much as on sight. When an alien drops from the ceiling and lands behind you, that's the only way you'll have a chance.