I just finished watching season three and it was exceedingly better than I remembered*. In fact it is likely the best season of Buffy. However my favorite season is season two. Spike’s a badass, Sarah looked damn hot and wore those great tank tops, there were some great individual episodes and it just fills me with a nostalgic feeling.
Season one was cheesy, but in a good way. I also loved how each episode's horror theme was an allegory about high school. I'm sure if I went to high school, I would have loved it even more (I should have been in grade nine at the time).
*Interesting how our memories work. Each time we remember we alter the original memory. So in a sense you only remember something once, and then you remember the altered memory. After eight years I only remembered the things I disliked about the season, like the awkward party scene, or the fact that Sarah had too many colors in hair through the first few episodes, or Willo being a 'wicca'.