Gosh, this is hard!
I had to go with Season 5, because it has my favorite couples, and my favorite Scoobies in it (pretty much amounts to the same thing...but I just really love this particular ensemble...all of them, not just the couples.

) I love seeing Xander and Anya, and Willow and Tara together, and happy, and minus so much of the dark icky stuff that comes along later. And Spike is in the middle of his long arc, mooning after Buffy and breaking my heart every other episode....the ends of Fool for Love and Intervention are just so touching.

And the final scene in Family, at Tara's b-day party, is possibly my favorite scene ever - everybody's there (except Spike) and they're all happy, and friends....and we don't get to see a lot of that. I love to see them all together, and having fun, and at (relative

peace. And then there's that beautiful dancy floaty thing....Also, it has Fool for Love, The Body, and The Gift in it.....three of the best episodes ever.
Unfortunately, I think Glory is the Crappiest Big Bad since The Master...

but it still wins it for me. And Unlike so many other people, I like Dawn. True, I don't love her as much as I do the rest, but she is a sympathetic character to me, and I certainly don't hate her.
I think Season 6 would come next, because by the end of season 5, I'm so entirely drawn in that there's almost no difference to me.....it's one continuous story.
Season 7 has my favorite Spike stuff (which carries a whole LOT of weight with me.)...I've loved Spike from the first time I saw him in School Hard, but I'm a total sucker for souled Spike. His arc from beginning to end just amazes me....actually, apart from the Spike storyline, I think 7 is likely the weakest season, and they were right to end it before it became tedious.
The rest are all pretty much even to me, overall. But I do have to agree with you taraswizard....The Mayor was hands down the best Big Bad ever. And Graduation Day was the best finale......when all those kids pulled those weapons out from under their graduation robes and prepared to stand and fight.....I thought I was going to die!!
What a rush!! And the "Class Protector" award a few episodes earlier makes me choke up every time.
