Unreal II is a good game if you don't look at it as a follow-up to the original game. Unfortunately, it is, and in that way it is completely disappointing. Unreal II looks better than it's predecessor, but the gameplay is inferior.
The protagonist, John Dalton, moves incredibly slow and thus it's pretty hard to avoid incoming projectiles. He also talks a lot and it's very annoying. The game is full of little jokes which are sometimes funny, but other times Dalton's voice is just so annoying you just want to mute him.
Designwise the outdoor areas look good - They aren't as jaw-dropping as the (pretty basic) outdoor areas in Unreal (1), though. Most of the time you are in pretty generic locations - Think hi-tech labs and all that stuff. There are a few exceptions, for example in one level you'll find yourself in the inside of a living, organic planet.
The game doesn't get overly interesting until the last levels, unfortunately. The final level is easily the best of the bunch. The ending is pretty disappointing, though, but I won't spoil it.