Serious Sam was able to have a couple hundred monsters on the screen at a time. I think if anyone can optimize a game to run with huge numbers of entities, it's Carmack.
The last "purist" FPS I can think of that had a good singleplayer mode was Serious Sam. Lots of enemy types (none of this same-kind-different-weapon nonsense). The problem was a lack of gore. Sure, there was some blood, but it looked fake and cartoony (except for hippie blood, which was awesome). A bit more blood and realism would make it better.
Dang, now I want "hippie blood" in Doom 4.
The last "purist" FPS I can think of that had a good singleplayer mode was Serious Sam. Lots of enemy types (none of this same-kind-different-weapon nonsense). The problem was a lack of gore. Sure, there was some blood, but it looked fake and cartoony (except for hippie blood, which was awesome). A bit more blood and realism would make it better.
Dang, now I want "hippie blood" in Doom 4.