Diablo 3 solo/campaign mode.

I've never played Diablo, but I decided to start Diablo 3 but with the campaign and solo. I don't like playing multiplayer and well. I find the story quite entertaining (without being wonderful) with an interesting lore. I know that many like 1 and 2 more, but 3 seems like a very fun and playable game for 1 player. I'm going through act 3 with a barbarian in torment mode I. I started on difficult and as my barbarian becomes very strong I increase the difficulty.

I'm liking it so much that I will soon buy the IV

What do you think of 4 compared to 3?