I liked 2 a lot. I only played through it once though, so I can't say for sure but I think I still preferred 1. I've been meaning to play through 2 again. I really liked the anti-gravity stuff better in 2 though.
As for 3... I didn't like it. I wanted to. I didn't mind the snow or the humans. What I didn't like was how the game itself played out. So much of the game was about things just running at you full speed which defeated the original concept of "Strategic Dismemberment" in my opinion. In DS1 you DID have moments like that but a lot of it was about staying calm and taking a moment to focus, think about which guns to use and landing critical shots. A little bit of patience in a panic really paid off more than just Spray and Pray. DS3 felt so much like just HOLD DOWN TRIGGER, take the hits, then pick up health because so many times I would move very cautiously, always check my back and then they would come up out of the ground behind me while others appear and run straight in. It got so annoying that I stopped and loaded up DS1 just to be sure I wasn't wrong about how things USED TO BE. For a minute I wondered if maybe it was always like this but I'd forgotten. Thankfully I wasn't crazy. DS1 was still just as fun as I remembered with a very different combat scenario. They'd definitely changed the game. And maybe it was better on Normal or something I don't know. I always like playing on harder difficulties for the sake of ammo conservation and less health. Perhaps the enemies behave differently on Normal which would have solved the frustration. Can't say.
I didn't like the reduction to 2 guns. While it's true each gun was basically like 2 guns combined for a total of 4, it still wasn't nearly as good as 4 separate guns with an alt fire each. And I REALLY disliked the shared ammo system. That was the whole fun of it. Running out of ammo on one gun, or trying to make sure you saved certain ammo for certain situations.
If I remember right there was some sort of really annoy love triangle going on and Isaac seemed way less likeable. Granted I only beat it the one time so MAYBE my view could change on a second play through. It's been a long time. Been meaning to play them both again. But right now the only parts I remember really liking in 3 were the snow itself, the repel rope and the parts where you are flying out in space.