As much as I enjoyed Borderlands 2 and The Pre-Sequel, most of it came from Handsome Jack's VA and the fact that I was playing them couch co-op with my best friend.
The original game, clunky and unpolished as it may be, is really the best overall game. It was simple, tonally consistent, and just a fun, enjoyable shooter you could put 30-40 hours into by yourself (or others) with a twist ending.
Everything after has been beating a dead horse, quite literally in some cases. I have not played Borderlands 4, mind you.

You’re playing it.
Borderlands 4 is really good though, all of them are playable except for 3