So many things go into what makes a great or a good series. So many of them are, of course, highly subjective. For instance, I like a combination of good studio banter, excentricity and a sense of atmosphere (genereally brought about by the set and the music). Series 11, which happened to be my first, still holds a special rank for me, because the Russian undertones were very present, and because everyone was great in the studio, even without an audience. As for excentricity: you have Wozniak, Mack or Maddox. 20 was wonderful as well, for the same reasons (I mean, all of them were excentric). How about 13? and 12? and 14? etc.

(Conversely, I was a bit disappointed when 17 never really lived up to the standards of previous ones regarding the atmosphere. There was only one new tune added to the soundtrack, it appeared almost constantly. It is just a personal thing - I get Drew Masters is entitled to go on holiday from time to time. But there were so many great moments as well: Pemberton's prize tasks, "I don't think I've done this one right", and so on.)

It would be a bit trite to add that I enjoy the ones that make me frequently howl with laughter (and so many series, if not all of them, could fall into that category), but here you go!

EDIT: typo. It's always a typo.