Buffy season 7 started off strong enough. I'd say the first 10 or 11 episodes were really good. But once the Potentials had arrived and were playing slumber party in Buffy's house, and after Buffy killed the first Ubervamp, the show started to spin in neutral for several episodes. It kinda lost steam. The arrival of Faith and Caleb helped ramp things back up towards the end but the pacing of season 7 was really irratic. The finale itself was pretty good but went by way too quickly.
Angel was the opposite. Season 5 really started off weakly. The series didn't seem to have a sense of focus. The characters were dealing with what seemed like random one-off villains of the week while they adjusted to life at W&H. It wasn't until the second half of the season that things really began to pick up.
Dollhouse really doesn't even belong in the same category as these two.
I'd have to say that Angel had the better final season, since it ended on a stronger note.