It seems like I am unable to convince anyone that Marathon 2 looks ugly.
Here is Marathon 2 with 1024 x 1024 textures on at 1080p

That blue looks like mold, but why are all of the walls made of elevators?
The textures that reach into the goo have no effect from said goo.
That yellow is clearly a Water / Sewage texture.
Here is Marathon 1 with 1024 x 1024 textures on at 1080p

This looks like something on an alien ship. Now again, in the context of M2, this is ridiculous, but you could tell that Dujour was dedicated to making an atmospheric, very evil looking alien ship. Not PeeWee's playhouse.

This is the worst looking room in any Marathon game, bar none. Every single texture in this room is just wrong. There is no form or cohesiveness. The angles make the textures stop at weird intervals, like the purple tiling is sticking into the yellow gate.

I'm not saying this is the best looking room, but you can see the cohesiveness. The earth tones, the lighting, everything comes together and it feels like you are actually in a hallway.

Again, goo resistant textures that also end up on walls. The simplistic patterns are like repetitions on your eyes, and also it's kinda big for a pfhor room.

What do I need to say? The dullness contrasts with the earth tones, the walls are like curtains, you can tell this is very cultured, do I need to point out the obvious geometry difference here?

LIQUIDS. DON'T. WORK LIKE THAT!

This is in my opinion, the most iconic look of Marathon. It screams Dujour. If you asked anyone whose played Marathon what raised zigzag crosswalks over green lava brings to mind, it's Marathon.
Marathon 2's pfhor levels have the geometry of a Sewage level, but the color palette of Pathways into Darkness.