Why are classic FPS games praised so much that they're considered as the pinnacle of FPS genre by their fans? While they do have more freedom and non linearity compared to their modern, more cinematic successors, they by no means are without flaws in my opinion. Flaws that I'd address are:
In classic FPS games, you get a bunch of guns, a handful of ammo, armor points, and that's it. You don't feel much more powerful than when you first started the game, only now you have a few more guns and probably more armor, of which will quickly vanish away. Unlike RPG games that make you feel significantly stronger than you were before.
In RPG games, visiting a dungeon that kicked your ass back in level 1 as a level 50 character makes me feel like a badass. So is beating an enemy or clearing a place that is not supposed to be beaten at your low level and getting a lot of precious loot. This doesn't exist in FPS games. There are no enemies that are far stronger or weaker than your character. This makes beating them feel much less satisfying. I think linearity hurts most action games as well, not just FPS. I think it would be great if FPS games had overworld and dungeons.
I've always wondered why I'm not allowed to carry medkits in my pocket while sacrificing some of my ammo or my guns, or why I'm only allowed to carry 50 rockets and 200 pistol rounds. Classic FPS games force us into that limitation.
This is more due to technological limitations, which is unavoidable, but my question is why do these shit gunplay and even graphics persist even in classic fps inspired contemporary fps games???? I'm looking at you Serious Sam. Just imagine how much blood splatter system, realistic body damage system (like in Soldier of Fortune 2 and the likes), and physics based response animation (just like the one in GTA IV) that are very accessible with modern gaming platform would improve classic FPS games. Or weapons with realistic handling physics, sound effects, and looks. Brutal Doom showed how much fun would it be to have realistic gunplay and gore in Doom, but it wasn't enough, graphic cards today are capable of full 3D graphics.
I mean, finding 3 keys for the entire game??? Jesus, you can do better than that.
Maybe I'm just nitpicking, but it would be nice for an FPS game to have more complex AI and environmental objects, just like the ones we have in RPG games. Environmental interaction in Duke 3D was enjoyable, but we can go far more than that. Like being able to towns with inhabitants each with unique dialogue and interaction, item merchants, and side activities.
I'm not saying that classic FPS games are bad, but they're definitely not the perfect example of FPS games. With our current technology and advancement in video game design techniques, there are many ways to improve their outdated formula.