Doom II is just more Doom I which is great! It has all the great things from the original game, like the buttery smooth movement, and fun combat. I felt that the level design improved a tad from the original, except for the levels after "The Chasm" (I honestly liked the Chasm) those levels weren't very great in my opinion, since they either had an annoying gimmick like darkness or confusing areas in them.

The new enemies were alright other than the pain elemental and the archvile, they were TERRIBLE. The pain elemental just spawns endless amounts of lost souls which were a very annoying enemy in the original Doom, and don't get me started on how terrible the archvile is.

I think I liked Doom II more than the og doom, but not by much.