Basically the event episodes: Day of the Doctor, the season finales from the Tennant era. There's no iconoclastic motivation in that, I just prefer a good idea well executed than a contrived event full of sound and fury.
Look at this poll:
http://www.radiotimes.com/news/2015-...s-voted-by-you
What a dull and predictable list. Were they really the best episodes? Or were they the most
memorable ones, because something big continuity-wise happened in them?
Bad Wolf is not too bad, once the Big Brother stuff is done with, but all of the other finales I found barely watchable.
Day of the Doctor is just an average episode. Not one of Moffat's better ones, but of course, with so many people watching it and in watching it in an uncritical mood, because it was the anniversary, it was going to be popular.
I think forums prove one thing: a lot of people watch with a pre-conceived notion or opinion and whatever they watch isn't going to alter that opinion

And I would say that is the case with Day of the Doctor.
Other than those I dislike all of the multi-Doctor stories, with the exception of 'Two Doctors', and even that I like mainly just for the wit of Robert Holmes. Again, they're event episodes, what we would nowadays term 'fanwunk' (sic). The stories usually don't make sense and the Doctors don't behave true to their original portrayals. Again, I prefer an interesting idea well executed to gimmick episodes.
I don't know if you could say it's a hugely popular Doctor Who episode, but from recent years I found 'A Town Called Mercy' to be unwatchable rubbish. I couldn't believe the positive reaction it got. It's a good example of why I never unequivocally recommend Doctor Who to somebody because there's always a chance they will try it out and see an episode like that, and I just cannot bear the thought of someone watching that and thinking 'Tom likes
this?! I thought he was a tasteful, clever guy...' :P
One more for the road... 'The Waters of Mars'. It's just a great exemplar of what I regard as the worst traits of RTD's writing. Don't get me wrong, he's a very good writer, and there's stories of his I really like (my favourites are Midnight and Love & Monsters), and I think he was fantastic for the show, but he has some characteristics in his writing just not to my taste and that episode is probably the most egregious.
Just one more... classic era: why do people love 'Terror of the Zygons' so much? It's okay but one of my least favourite episodes of possibly my favourite Doctor Who era (Baker, Holmes and Hinchcliffe). I don't dislike it but I can't see what it does better than say, Planet of Evil, or the Android Invasion, or some other similarly unheralded serial from that era.
Disclaimer: I don't 'hate' any of the above episodes; a bad episode of Doctor Who is hardly cause for consternation; the above is all, of course, just grist for the forum mill.