Don't I remember doom developing pretty organically from wolfenstein and a few other (what would now be called) first person shooters around that time? The name "hexen" is coming to mind too. I would put that whole era as the start of something new, so different from the strategy games and side-scrollers that preceded it. Those first person games were the first time I thought computer games were actually more fun than the console systems, which didn't really have anything similar.