Similarly, I went off WoW as soon as The Lich King expansion came out, just as I did as soon as The Burning Crusade came out. Somehow, Blizzard just managed to -TOTALLY- fuck-up almost everything good they did in vanilla WoW.
LUCKILY, I gave Cataclysm a chance- thank god I did. I love it, and I rarely loved WoW even in the beginning. They have COMPLETELY redone everything.. gutted it like a fish. They got rid of almost all the crap, (of which was a legendary amount) left all the good, and added a lot of great things.
It's like Vanilla, but a lot better.
Everything- from 1-85 quests (which all feel awesome, epic, great storylines and all), cutscenes all the way through, the sundered world looks stunning, I haven't tried Worgen (I am Horde), but the Goblins have taken my heart- love them to death. Races have new classes attached, new talent trees. The dungeons/heroics (I haven't hit the raids yet)- are absolutely immense. They are MUCH harder, require a lot of patience and tactics, but are really fun.
So all in all, Cataclysm is the 1 thing that WoW needed to survive, and did it spectacularly. It's finally got me interested.
EDIT- as per the poster above me; I agree. WoW really is almost all about the community. No matter how good the actual game is, being an MMO- a lot of it revolves around other players. If you have a bad server, full of a-holes, no good guilds, it can be really dull & depressing. You have to find somewhere to -fit in-, I guess you could say.