yeah however they were 2d sprite enemies - the 3d was non existant in those games...
Once you talk about mapping polygons to creatures, applying bitmaps and have 3 dimensions, it gets harder to do anything with class.
I don't actually look forward to ID games just for the gameplay - i look forward to the new technology that everyone in its wake starts using.
e.g.
Doom 1,2- 2.5 dimensions however monsters were still sprites and used soundblaster wave files for awesome sound effects (well at the time they were lol) - Duke 3d and clones copied. thousands of enemies, easy to do coop (cause the processor could handle throwing sprites around - they were basic!)Serious sam used the above techniques - 2.5 dimensions.... however the bitmaps on these sprites were a lot nicer in the period. ID were busy after its doom games creating a new technology so everyone had time to release new and improved versions of what ID had already bought out.
Quake 1,2- 3 dimensions and polygon monsters , start of the bitmaps, nine inch nails sound effects+ the great console commands (which MOST games copy now but can't get half the commands in which ID gives out)- half life and clones copied. Problem everyone complained about - not enough monsters...
Doom3 - Ultra high polygons rendered on awesome machines to get great looking models and then they scale em back for slower machines . Reverse engineering to cope for todays' processors (brilliant idea). Creatures have bumps/ripples that can be effected by where the light is. NO GAME CAN REPRODUCE THIS TECHNOLOGY!. (yet cause when it comes out- everyone will then copy)