My favorite Season will always be 2. The episode sequence of "3 sundays, The new girl" and "Maidenform" is what made me fall head over heels with the show. The writting on this show is always phenomenal, but I thought in this season it was especially good. I loved Peggy's, and Betty's stpry arcs this season especially, and the show still had that early 60's old fashioned patina, which I can't help but miss. Also, Bobbie Barret. I adored her.
Season 4 would probably come next. I liked the new, exciting, feel to this season, with the new agency, and Don as a bachelor. Don's whole downward spiral was enthralling, and it's the first time we ever got to see him become really pathetic. The new characters were great (especially Miss Blankenship, Stan and Faye) and it also had really amazing episodes. My only problem with this season was that Betty was literally written as a villain, which I hated.
Season 3 comes right behind it. I thought the writting, or should I say, dialogue, wasn't quite as great as the first 2, but plotwise, it was amazing, with Betty's discovery of Dons identity, the break up of their marriage, and the creation of the new agency. Just great stuff all around.
Season 1 was very well written, but maybe because we hadn't got to know the characters all that well and hadn't had time to warm up to them, that it seemed the season went a little slow. That being said, the last 2 episodes of the season were amazing, and if it wasn't because of them I may have not bothered to continue watching the series. Not that I thought the show was bad before that, just a little cold, and boring.
Season 6 would be next. While it was evident to me that the show just wasn't going to be as excellent as it had been seasons 1-4, I did find it a step up from S5, and I thought the adding of a few new characters, like Ted, and the merger, livened things up a bit, and brought really new, and interesting character dynamics. I thought Sylvia was a bore, but I liked Arnie alot, and his friendship with Don. I also loved the end of fat Betty, and the Betty/Don "reconciliation".And Megan no longer ate the show.
Season 5 is still my least favorite because of Megan, and Megan and Don eating the show. I never found her interesting, no matter how the show tried to make her so. I also wasn't a fan of the "Joan sleeps with Jaguar" storyline, I thought it was soapy, melodramatic, and that it didn't fit the show. It felt like something out of "Melrose place" or something. Also, Fat Betty pissed me off, because it seemed like a meta dig at her character. There were a few excellent stand alone episodes, like "Signal 30" or "Faraway Places", and a couple of others, but the season as a whole left me sort of cold.
I will refrain from ranking this past mini season because it really didn't feel like a complete season to me.Based on these first 7 episodes it would probably go somewhere between season 6 and 1.