I liked Deus Ex 2 personally. While it was inferior to the original I still enjoyed the story. The only problem I had with that game was getting it to run on my PC. My computer met all the system requirements and it still ran like crap.

The first game that came into my head when I read this thread was Devil May Cry 2. The enviorments were dead. The character designs were lame. The in your face action that the original had was replaced with fights taking places miles away from the camera to the point where you could hardly see what the hell was going on. And Dante became about as interesting as a sack of potatoes. You could tell they put as little effort as they could into the game before release, and it showed. The series has never really been the same since in my opinion.