Hmm, Doom 3. Initially I thought it was really cool. Amazing graphics, atmospheric, made you jump occasionally etc, but I am getting bored already. The main problem I have is actually the predictability. After you play for a while you can predict where monsters will spawn and how many. For example, suppose an imp spawns in front of you. You immediately know that one will spawn behind you as well.
Also, the fact that monsters keep spawning in areas you have just cleared gets really really annoying after a while. Whats the point of securing an area just for more monsters to spawn? Ok I can live with imps etc arriving as they teleport in, but where do the bloody zombies appear from? Again this makes it predictable. If a monster appears in front of you, you can be damn sure one will appear in the just cleared area behind you.
Hopefully Half Life 2 will be less predictable.