I've played every Doom game besides this one up until recently and I have to say I'm pleasantly surprised. The lighting, enemy, and weapon design are improved from Doom 1&2 and on the hardest difficulty the game is quite challenging. If you are a fan of the originals, this is more of the same but with a little trickier puzzles and what I personally believe is better level design. I would put the difficulty on par with Doom 2.
I know the soundtrack is kind of a divisive subject in the community because it abandons the heavy metal inspired midi chiptunes from the first 2 games in favor of a more ambient dark soundtrack but in my opinion it evokes a more horror/ dungeon type feeling to the game along with the improved visuals. Some fans might not love it but I think it fits really well with the dingy environments and labyrinth-esque levels.
Speaking of levels, the levels look great and are packed with detail and variety compared to the first 2 games. Regardless of how you feel about some of the enemy redesigns, there is a lot more detail in the bad guys. I think the enemies look scarier and more aggressive/ intimidating although I will say they look more alien-like and a touch less demon-like in some instances such as the Imp. Nevertheless I really like the visuals of this game and I came to appreciate the dynamic lighting. It's a shame I never got to experience this on the Nintendo 64 because I'm sure it was pretty groundbreaking for it's time.
I also think tonally and thematically this game does a pretty good job of bridging Doom 2 and Doom 3. What I mean by that is if you played all 4 original games in a row rather than jumping right from the frenetic, colorful, fast-paced style of Doom 2 to the much slower, darker, horror-centric Doom 3 this game feels like it's smack dab in the middle. Even in the small bits of exposition we get, it seems like the game takes itself a little more seriously than Doom 1&2 and it's a little surprising that the original id Software team did not make this game. Doom 64 plays like a happy medium between the original trilogy without losing the feeling of the first 2 games which I think is interesting.
There's actually not a lot to say negative about this game (especially for $5) but If I had to pick a couple things I wasn't in love with I would say my first gripe about this game is that there are many trap type elements where falling blocks can crush you instantly or floors that disappear out from under you are frequent. In the original 2 games this would often take a large chunk of your health, or in the case of a trap floor going out from under you, there would often be a safe spot, teleporter, secret switch to lift the floor, and/ or a radiation suit. You would survive but you'd be punished for your carelessness.This game seems to revel in it's "gotcha" moments where you fall for an item placed suspiciously within reach and when you go to collect it the game traps you into insta-death situations for assuming a power-up might be a reward without a consequence. This becomes a mental game of "Is this a trap or is this game preparing me for a big boss/ arena fight?" and sometimes it isn't very obvious which circumstance you're in which can unfortunately put you on the backfoot when you decide not to take a power-up that wasn't actually a trap and you end up in a serious fight without that Mega Armor, Soul Sphere, or Mega Sphere that would have really helped you out. It isn't the worst because you quickly learn to save your progress often but I will say the gimmick got a little annoying after a while and loading saves where otherwise I was doing quite well in a tough mission got a little irksome. It is a little frustrating to be armed to the teeth with over 100 health and armor and then die to some silly trap. It had the unfortunate effect of teaching me to ignore all major powerups and to instead just rely on regular armor boosts and health packs. No part of the game seemed to necessitate an invincibility boost or a Mega Sphere so it wasn't the end of the world.
I also never got over my annoyance with the lack of gun animations. I will say, the guns sound GREAT and most of them look terrific. I especially liked the revamped look of the Plasma Rifle, the Rocket Launcher, the BFG, and most of all the Chain Gun. All of the weapon audio is terrific and the shotguns especially are punchy and aggressive. That being said, the iconic pump action from the no-super shotgun is, for some reason, absent. As for the Super Shotgun the reload animation is entirely missing. Instead what you're left with is audio queues to let you know the Shotguns are racked/ reloaded and ready to fire. It is a slight grievance I know, but it seemed like with all the improvements to fidelity it's a pretty glaring issue to not include on a double barrel shotgun that used to have a rather cool reload animation and now just magically regenerates shells in each barrel. This probably won't bug people nearly as much as I'm imagining.
If these seem like minor complaints or that I'm splitting hairs it's because I am. I genuinely think this is a terrific game and for the price, whether you're a Doom fan or not, it's a lot of fun and a good value.