I prefer marathon over doom, for gameplay wise.
Engine is reall good in comparison. Then again, it was released around when doom2 was released, so they had an extra year to cook the engine.
Gameplay has the killing monsters from doom, run into rooms full of them and clear them out style, but it has ammo conservation like half-life and a story-telling structure like…marathon. Besides the HL2 mod Minerva (Inspired by marathon), no other game has a story telling structure like it.
Actually, I probably like it as it plays like half life, if the half-life doom mod were to be remade, the marathon engine would fit it perfectly, wall health/armour chargers come with the engine, it can also cope with the room on top of room that Doom lacked (But not floor over floor).
Also, back when I was 6 it felt so liberating to look upwards in marathon, where doom was lacking that. Quake was the best for that also, but due to quake actually being 3D it is a different comparison to make.
I do play Doom1 a lot though, on Wii. My girlfriend loves it still.
I got this Doom3 mod which remade the first episode of Doom1, it was no Black Mesa, but it was alright. It was scarier than Doom1 due to the new enemy AI, and only because of the new AI.
Doom2 I really can’t get into, it just seems too rectangular and blocky compared to doom1, like, everything in Doom2 had a purpose to the levels, in Doom1 there were more side-rooms and explorable bonuses, Doom2’s secrets weren’t as fun to find.