For me the best seasons are 2 and 5. Season 5 is really where the central metaphor of the show found its feet and took hold (that adulthood is rife with selling out and compromise), and it's a crime that it was cancelled after that - especially since the ratings went UP by about 20 percent.

I do love Season 2, though, for the whole Darla and Drusilla arc.

I'm working on a meta about what made Angel groundbreaking at the time. Nearly every article I've read recently completely misses the mark.