This is such a great idea for a thread! I'm going to be spending years checking out your favourite shows.
Glad to see the Prisoner turn up so much here. When I was 15, I watched Twin Peaks and the Prisoner in the mid 90s on the Bravo TV station, and both blew my mind. Nothing has ever come close to those two, so my top ten would be:
Joint 1+2: Twin Peaks, The Prisoner
3. The Prisoner
4. The Prisoner
5. The Prisoner
6. The Prisoner
7. The Prisoner
8. The Prisoner
9. The Prisoner
10. The Prisoner
The Fall and Rise of Reginald Perrin: By far the cleverest British sitcom ever made, and much greater than lesser works from the 70s that get all the attention (I'm looking at you Fawlty Towers). It's about a businessman having a nervous breakdown, featuring a legendary performance from Leonard Rossiter, and it is by turns tragic, funny and touching. The best satire of corporate life there has ever been, and writer David Nobbs is a genius.
Minder: Classic, long-running satire of Thatcher's Britain with George Cole and Dennis Waterman as cockney spivs. At its best, its like an 80s take on Ealing comedies every week, and I prefer it to the similarly excellent Only Fools and Horses. I even liked it after Waterman left.
Still Game: This list is making me realise that, outside of 1-10, I really love sitcoms. This Scottish gem is the finest British sitcom of this century. It's a completely unsentimental look at the life of pensioners in Glasgow, and it is superbly written and performed in addition to being very funny indeed. Some episodes just floor me in terms of every creative choice being exactly correct. Like most long running shows, people feel it tails off towards the end, but I've nearly finished all 9 series and am still enjoying it.
Dr Who classic era: already covered above, and it's just essential TV for my generation. I don't mind the remake, but I didn't watch it as a kid, so I can't love it as much as the classic era. There is a charm of the classic era that the modern one doesn't have.
Start Trek TNG: Also covered above. I never saw this in the 90s, because my pesky Dad insisted on having the news on on BBC1 instead. I've watched it as an adult, and I completely fell in love with it. Patrick Stewart is insanely brilliant in it, and I realised to my amusement that I actually fell in love with him a bit when I first started watching it. I was spending days in the office looking for interviews with him, and just loving everythin he ever said and did! I still wonder what Picard would do when faced with a tough choice.
Kids in the Hall: Glorious Canadian humour in the vein Monte Python. Deeply surreal and amazing.
The Bureau: brilliant recent French spy series that is super realistic. Takes into the life of the modern spy in incredible detail, and the politics are also very believable.