Doom 2's my favorite. That tired vibe it gives off after the mediocre Icon of Sin battle always makes me smirk, even if I've seen the same ending for so many years.
I've been replaying Doom 2 recently, and I've started appreciating the odd texture choices, as well as the strange - in my opinion - level design. I've also realized that I prefer 2's soundtrack compared to Ultimate Doom's.
I don't exactly remember my age at the time, but I did have a very strange family member who was obsessed with the occult who thought the game looked interesting - because of the satanic imagery I'd assume - anyways he let me play it for a bit before telling me to get lost. I like to think that's when the seed was planted for me to enjoy le Doom.