I rank em 2>5>3>6>4>7>1
I seem to be one of the few people here who really digs Season 6, so I'll put in a little word in its defense.
- I think 6 is by far the most ambitious season. They really swing for the fences with a lot of what they're doing. Some of that works, and some of it doesn't, but you've gotta admire the guts. And what work REALLY works and hits on a deep emotional level.
- Case in point: "Once More With Feeling", which is a brilliant and super-gutsy piece of TV. It isn't content to just be "the musical episode", but it's also the episode where Buffy reveals she was pulled out of heaven, and the episode where she kisses Spike, and the episode where Tara learns Willow cast a spell on her, and the episode where Giles decides to leave, etc. It's incredibly ambitious, and they totally knock it out of the park.
- Buffy's resurrection is handled really well. I absolutely love the idea that Buffy wasn't saved from Hell, but ripped out of Heaven. It's an inspired twist on the idea, and sets the groundwork that Season 6 is really about trying to figure out how to deal with life. Not just grown-up, adult life, but just life itself.
- A lot of people don't like The Trio, but I never had a problem with them. They complement the main theme nicely as these guys who are living in a fantasy world, and don't react well when real life intrudes on them. Plus, they're funny comic relief (in a season all too lacking of it), and Warren's turn to completely awful human being is one I totally buy.
- There are a ton of great, memorable moments in 6. A lot of my favorite individual moments from the show come from this season. Willow's confrontation with Giles in "Flooded", All of "Tabula Rasa", Anya's slow walk down the aisle at the end of "Hell's Bells", Joss Whedon doing his own Dark Phoenix story over the course of the last 4 episodes, and my single favorite Buffy moment: "I'd like to test that theory."
- "After Life" is, in my opinion, the most underrated episode in the series. Nobody ever mentions it, but It's in my top 10 episodes. It does a great job of setting up all the different plot threads of the season, and features some really great creepy moments (in particular, when Anya gets possessed). It's also the best that the Spike/Buffy dynamic ever got. The moment when Spike sees Buffy for the first time and realizes that she isn't the Buffybot is really powerful, and then the scene later in Spike's crypt always gets me:
Spike: "I do remember what I said. The promise. To protect her. If I'd done that, even if I didn't make it, you wouldn't've had to jump. I want you to know I did save you. Not when it counted, of course. But after that. Every night after that. I'd see it all again, do something different. Faster or more clever, you know? Dozens of times, lots of different ways...Every night I save you."
The only problem with the episode is the lame CG creature Buffy ends up fighting, but I'm willing to forgive that for all the other goodness in the episode.
- I admit, the season has problems. The "magic = drugs" storyline with Willow is not very well thought out, and the Spike/Buffy relationship is really problematic. It also really sags in the middle. I really like the first 8 episodes and the last 7 episodes, but the middle 7 are pretty rough. Still, the high moments make it worth it to me, and the emotional beats (particularly the way it ends) really stand out.