In Season 1, the strong ones are Welcome to the Hellmouth, The Pack, Angel, The Puppet Show, Prophecy Girl. The moderately good ones are The Harvest, Out of Mind Out of Sight, Nightmares. Loserville is populated by The Witch, Teacher's Pet, Never Kill a Boy on the First Date, I Robot You Jane. The problem is you get a strong first part opener, a weaker second part and three of the losers right together after that. Once you get past the monster of the week slump near the beginning, you have good viewing after that.
Season 1 is often picked as one of the worst but a lot of other seasons do not have as high a proportion of good episodes. For me, Season 4 is the worst. In the regular one episode a day watch of the series, I got bogged down at the Initiative.