Disclaimers: I played on the easiest difficulty, and don't regret it. I also had to restart after getting 2/3 the way through the campaign due to a corrupt save file, which coloured my experience a bit. I have never played a Doom campaign before.

I have played Doom campaigns before. I also played on easy.

Mechanics:
In almost every way mechanically, this is the best FPS I've played since Halo 3/ODST. It takes all the crappy modern-day staples that have been leaking out of CoD into other franchises, and tosses them out the window.

I agree.

I do have a few quibbles- the vertical jump sucks, and the upgrade you get half-way through the campaign doesn't improve it much. Mantling is spotty. The starting guns become completely obsolete very quickly.

How dare you, I think those were great.

...But dang near everything else is so good that it makes up for it. Again, I haven't seen Enemy AI this fun to fight since the elites in Halo 2, or the hammer brutes in Halo 3. The run speed is the perfect balance of fast and controllable. The Guns- oh man, the guns! I never realized how much of a detriment reloading is to the flow of combat, and now that I've seen the other side I don't know how I'm going to go back. ADS is only used for guns that have scopes, but never required, much like Halos 1-4.

Same. Except Elites in Halo 1 -> Destiny Fallen -> Doom bad guys.

Level Design:
Some good, Some not so much. I think I just don't like wandering around a maze-like level after having killed everything, trying to figure out where to go to progress. Classic DOOM fans will probably enjoy that more- I had more fun when the path was obvious, and I wasn't spinning a 3D map around. Arena encounters were fun. Boss fights were a bit "meh".

Accurate, but I knew what I was getting into. That's pretty much doom. It's also my least favorite part, but it was much more acceptable in the 90s.

Story/Mood:
Very compelling. This is about the amount of levity I wanted and got out of the first three Halo games. Codex entries are great, much better then the Grimiore in Destiny (and I don't even have to open a web browser!) Narrative is a bit simple/predictable, but simple is better than confusing or cliche. I'm not big into heavy metal or gore or the occult, but again I know that the intended audience is looking for that out of a DOOM game. Sci-fi stuff was fun, and I like the way that part of the game looks.

Same, except I am into heavy metal, gore, and the occult. I thought that stuff was the best part. Classic!

Final thoughts:
I hope other FPS games take as many cues as they can from this game (mechanically), including Des2ny. They set up quite a few loose ends/narrative hooks throughout, so hopefully those pay off in the sequel.

I don't know if other games can at this point. One of the things Doom did was go anti cover shooter. Low on health, the way to get it back is to do a close quarters attack on the bad guys. No reloading, etc. We'd have to see new shooter franchises come from this. I don't think Destiny 2 will incorporate much of Doom's feel or features, and they shouldn't, either. They're too different.

Glad to hear you enjoyed it so much! I just picked it up myself. Doom and Titanfall 2 both get thrown around as examples of "the return of smart design & mechanics to the FPS genre in 2016" (- I'm paraphrasing, but it's a sentiment I've heard quite a few times from various critics and outlets). Hopefully we're seeing the start of a trend. I wouldn't expect most games to live up to Doom or Titanfall 2's quality bar, but maybe we'll at least see some more inventiveness across the board. The amount of attention given to the "Effect & Cause" mission in T2 alone shows that gamers are craving it.

On a semi-related note, I just started playing Gears of War 4 and I'm surprised by how much I'm enjoying it so far. It certainly isn't anything groundbreaking so far (I'm only a couple hours in), but the basic Gears mechanics are still rock solid, and it plays better than the countless 3rd-person cover shooter clones that have come along since the original Gears. There's also something to the design style of the world and gear and characters I enjoy playing in. Plus I'm having fun with the characters & story more than I thought I would. I doubt there's anything here that would convert people who haven't enjoyed Gears of War in the past, but anyone who was a fan in the past might want to check it out. Strong follow up so far.

Final thoughts:
I hope other FPS games take as many cues as they can from this game (mechanically), including Des2ny. They set up quite a few loose ends/narrative hooks throughout, so hopefully those pay off in the sequel.

Since others are finishing this game, I feel the need to comment on the end. Spoilers, obviously, but sticking the BFG in the final boss's face and pulling the trigger for a glory kill was hands down the most internally consistent and satisfying ending of any video game I've had the pleasure of playing. I roared laughing for a solid minute. Expectation utterly and completely satisfied.

Now that I think of it, in recent memory there isn't much other media that's come close to this.

Disclaimers: I really enjoyed Limbo, so my expectations for this game were fairly high, although I read a hyperbolic review by the huge fanboy Ryan Mccaffrey that helped remind me to temper my expectations. That said, I was able to go into the game completely unspoiled.


Mechanics:
Identical to Limbo, so if you played that one, you know the controls, the physics, the puzzles. Not a bad thing, since it's engaging and simple without slowing the pacing of the game. I love that you can see where the hidden objects are, and figuring out how to use the tools at your disposal to reach them is often more fun than the puzzle that you're supposed to be figuring out.

I do have a few quibbles- There is a bit of frustrating design where I'd often be triggering actions and animations with the Submersible that I wasn't trying to. And sometimes there aren't any context clues for what you can and can't do, so you might be the victim of a few unfair deaths.

Level Design:
The puzzles are often too simple, which again, is good for pacing, but it's really dumbed down compared to Limbo's "Aha!"-causing brainteasers. Other than that, the levels are never confusing, and the atmosphere is always really great. Moving from area to area does feel like a natural progression, and the hidden objects are always fun to get to. Honestly, I feel like the game should have placed a greater emphasis on needing to find them, if only because many people will miss out on some of the best puzzles in the game.

Story/Mood:
Everyone says to go into the game completely blind in order to avoid spoiling "The Twist™", but I'd say that it really doesn't matter, because although there are a vague number of puzzle pieces to stitch together, the final twist comes out of nowhere, and the game does nothing to earn it or have the puzzle pieces come together enough to paint a picture afterwards. On the flipside, the game does give you enough to work with that you understand and are willing to roll with the twist, even if it doesn't answer more than a couple of questions (and one of those is left for players to interpret), but it didn't come as much of a shock as it seems to be for some people, so I don't think you should bend over backwards to avoid a gameplay twist in a game with only vague hints of a story.

I did find all of the hidden objects, and got the "secret" ending before I got to the twist, so things kind of made more sense in that context, but again, I don't think most players will bother going out of their way for this extra bit of info (and it's a lot of work for a single important detail), so the story suffers just that little bit more for it.

Final thoughts:
While I enjoyed the experience, I wouldn't call Inside a "Masterpiece". Heck, I wouldn't even say that it's better than Limbo. But the atmosphere is fantastic, and once you get to the twist, you buy into it, and everything afterwards elicits emotion very well (I sure as heck didn't spare the director's life), which I can't say for a whole lot of games that I've played recently.

I'd give it a 7/10. Well worth the $9, but not the original $20 asking price.