How many new enemies will Doom need?

I think it's an important question to ask. The game seems like it will be making use of the full original arsenal pretty quickly, judging by the fact that we'll be seeing Hell Knights on the first level.

If the full Doom 1/2 roster ends up being used just a few levels in, will it be enough to carry an entire game without the experience getting dull and repetitive?

If the enemies that are in are varied and fun to fight, and there's a good assortment of enemy combinations in each fight, I think it'll be fine.
I would love every single enemy to return and some new ones, but if every fight contains 20 imps and a few other enemies, combat will become stale very fast.

It would be pretty cool to see some new hellspawn. Like the post above said, interesting enemies though. Maybe guys with shields that block all front attacks, like that one Quake 2 enemy; monsters that walk on ceillings or some other crazy shit like that.
One of the things that let me down about Doom 3 was that most of the new enemies were melee only, "get in your face" types. (the zombies are okay, but the spiders and cherubs are just too annoying for comfort)

I hope to see a lot of variants of the same monster as well. Not just a recolor, but a new skin! We see this with the mancubus/mechcubus. It will be good for SnapMap.

Marnetmar said:

The game seems like it will be making use of the full original arsenal pretty quickly, judging by the fact that we'll be seeing Hell Knights on the first level.

From where did you take the info that the level in that demo is the first level of the game? It isn't mentioned in the article.

Regarding the question I am with wheresthebeef: it's important that the monsters are varied enough.

The 15 (minus the bosses) monster types of Doom 2 are a good number. The 8 monster types of original Doom were too few, that's why alomst every custom wad uses Doom 2 as a base. Doom 3 also had arround 15 monster types, plus variations of the zombies to give them more personality.