I've been playing the remake of Rise of the Triad and, to be blunt, it's fucking glorious. Everything from the original is preserved, including all the ridiculous powerups, six different rocket launchers, jump pads, bottomless magazines, a movement speed that flips the middle finger at the whole concept of "taking cover" and, of course, ludicrous gibs. Also highly self-aware and self-parodying. All rendered in the Unreal 3 engine.
Speaking of Unreal, you might give that a go. It was the 1998 single-player precursor to UT99 and is very well designed and balanced.
Also Deus Ex, if you want something a bit slower with a very good story. Both the original and DX:HR are excellent, but the original's graphics have aged horribly. The voice acting in Human Revolution is also far superior.
I'd say System Shock 2 is also quite interesting.
Speaking of Unreal, you might give that a go. It was the 1998 single-player precursor to UT99 and is very well designed and balanced.
Also Deus Ex, if you want something a bit slower with a very good story. Both the original and DX:HR are excellent, but the original's graphics have aged horribly. The voice acting in Human Revolution is also far superior.
I'd say System Shock 2 is also quite interesting.