I beat Borderlands a few days ago and I felt the gameplay was kind of repetitive. Go here, kill those guys, get this item, bring it back was basically the whole game. After a while I kind of forgot there was a story to it.

On the other hand I haven't beat AC3 yet but the story is pretty good so far, lots of drama. Gameplay wise AC games feel the same only thing that changes is the weapons and setting imo. Not much else changed.