I had so much fun with this game. I even think this is probably one of the most fun 90's shooters ever. It's pretty much a party with bullets. And i even think that most of it's failures are actually what helps the game to be so fun.

Quake 1 has this dense atmosphere, that NIN soundtrack that makes everything more horror-themed, and those enemies that were actually kinda creepy, and
truly dangerous. Quake 2, instead, shows a really poor AI in enemies that aren't scary at all, while you go shooting around with the most-badass heavy metal soundtrack, so it's all about feeling good with no real challenge. And to me, that's fine. So if Quake 1 felt like a horror movie, Quake 2 is mostly a sci-fi rambo-like action film.

Weapons are overall better than Quake 1, and the level design is pretty much ok. Some units are actually very well done. i don't really mind about backtracking honestly, but that might be a bad thing for many.

In conclusion, you'll probably have much more fun with this game if you don't take FPS as if they were a competitive sport.