I played D2 at launch and got through the campaign and had a good time. Just like with MMOs, I don't care about the end game and just want to play the story.
Tried to come back a while later and discovered 'vaulting' and haven't fired it up since. I can't be the only one.
I liked the second game but can totally understand why some wouldn't. I'd say the first game is a western action game, while the second game is more like a cowboy sim. I find it much more immersive, but much slower paced.