I voted "Angel" as the best. For one thing, Angel became my favorite series overall and this episode finally let us know what the deal was with this guy. Angel throwing down with Buffy was good and I loved his line where he is telling Buffy about what he did and how he came to be and tells her, "For a hundred years I offered an ugly death to everyone I met, and I did it with a song in my heart." That is wicked poetry and a foreshadowing to his poetic style in Season 2 episode, "Passion" (I can't believe I am actually starting to memorize the episode titles).
Another fun episode was "The Pack" as gruesome as it was with the students eating the pig and the principal. However, it had its share of funny moments particularly at the end when Xander was talking with Buffy and Willow saying he'd no recollection of what happened. Then Giles walks up and the conversation goes:
Giles: I've been reading up on my, uh, animal possession, and I cannot find anything anywhere about memory loss afterwards.
Xander: Did you tell them that?
Giles: Your secret dies with me.
Xander: Shoot me, stuff me, mount me.
That was just a classic Xander moment and the interaction with Giles was hilarious. I had to rewind and watch Giles' expression as Xander walked away.
After those two episodes I would say "Welcome to the Hellmouth" and "Prophecy Girl" are pretty good.