Having (recently) played through every game, including a Ultra-Violence pistol start in all of Ultimate Doom and Doom II, my vote is for Doom Eternal. 2016 and Eternal are so freaking good. I love classic Doom's engine and enemy types more, but the actual level design is extremely hit or miss. The modding scene makes classic Doom far superior to the new stuff, but in terms of the actual products, I really loved Eternal. Tough as nails, but I really felt like I had to git gud and did, so it was a blast.

My vote goes to the first game because it's more impressive to invent the wheel than it is to refine it.

I will say that almost no 3D game from the 20th century has aged as well as the original Doom. It's no small feat for a game from 1993 to still play great in 2021, much less one from the formative years of the third dimension.

Definitely an all time classic to rank alongside games like Halo Combat Evolved or Super Mario Bros.

I actually first played in on the SNES and even at a very low resolution and around 15fps it was a blast.

Doom Eternal for me.

If this doesn't turn you on with Doom, nothing will.

Brutal Doom v20 Official Trailer - YouTube

Brutal Doom v21 - OPEN BETA Trailer - YouTube

Brutal Doom v21 Gold Release Trailer - YouTube

Well Doom didnt exactly invent the wheel

All i know Todd Howard didn't Balance Doom Eternal, So Doom 1993 for me

Doom 64

The first dooms were neat because they made 2d look 3D. But 64 was 3D. It felt real at the time and responsibly made me shut out my world and put in headphones to play alone. Boy was it creepy any intense. The sound matched the level that the graphics brought it to. It just got better and better every level. The fact it was on a console at the time! PC gamers scoffed at the idea that a console FPS was as good, but the 64 control was actually amazing! You could control forward/back/turning & fire with just the left hand — while the right hand hovered the left/right triggers for strafing. It was a marvel to have such fluidity. Newer dooms failed to capture the puzzle and atmosphere. 64 was ground breaking in the 3D era

My bad. Should have been more clear. I meant to say that it's always harder to create a brand new, successful IP than it is to refine one. 

Doom Eternal.

Way more fun than any other Doom games.

I would say:

Doom Eternal > Doom 64 > Doom 2016 > Doom 1 & 2 > Doom 3