Mine is only 88 replies; in fact, that’s my only thread to ever get a second page.
I suck.
(On the other hand, 92.6% of my posts have been to existing threads. Guess I’m not much of a conversation starter…)
The Doperball threads generally attract big numbers, with Doperball III topping out at 366 replies.
FTR, that other thread went to 398 replies, but since I technically didn’t start it, I’m not counting it here.
Obvious things about a creative work you realize after the millionth time started out so slowly I was sure it was going to die.
It later catch fire and made Threadspotting.
27 pages, 1331 replies, and for the most part only half a dozen posters, one of whom was Santo Rugger.
It was a RPG thread in The Game Room.
I don’t start many threads – just 31 so far – and my longest one was posted shortly after the Game Room opened: No Mornington Crescent yet? – 194 replies
My second longest was posted in The Pit, 5 years ago, and was just the third thread that I started here: I pit 46.6% of Australian voters – 130 replies
Got one going right now over in IMHO which looks poised to hit 7 pages. Doubt any of my previous efforts made it that far.
Who woulda thunk the key was to get folk to talk about what infuriates them? 
Mine usuall die in the low double-digits, but I’ve had three that have topped 300 replies. My 2006 baseball thread hit 375. Two Pit threads each got 300 or more (one on the Saudis, one on Catsix).
Couch to 5K: Anyone with me?, which is still going, and is currently at 420 posts.
Next runner-up was a Pit thread I started to question Evil Captor’s suspension, a few years back, with 378 posts. (I had totally forgotten I started that thread, until I searched just now.)
Hardly any of my threads have cracked the 100 barrier, though.
Search keeps losing me, but I once started a “line-at-a-time” limerick thread that went on for about 6 pages.
The still-active Job-Seekers’ Support Group has over 1,000 posts, unfortunately. I also started a game thread, Move Game IV, that went over 2,000 posts (2,014).
Things people do that you just don’t understand. Devolved into a “people you judge” and then “what are your pet peeves” rather quickly. 227 posts.
“Can America trust atheists?” got 447 replies - so close to that 10th page, but not quite. I’ve had two other threads get about half that many responses but most of mine were much shorter.
I have several that are of approximately equal lengths:
Over-rated Items from You Regional Cuisine- 230 posts, 6141 views
I Resent it When Strip Clubs Hire Fat-Ass Bouncers- 172 posts, 8488 views
What Was the Loudest FanBoy Howl of Outrage?-154 posts, 6643 views
Just the Punchlines, Please- 234 posts, 2402 views
Longer than this thread.
But not much.
Wouldn’t it be funny if this thread attracts well over a hundred posts? Anyway, I’ve started 2 threads that were about 80 posts long, but nothing amazing. Still, I wouldn’t be surprised if most threads on the dope never made it over 10 posts.
Mythbusters: Hindenburg - only 64 replies, but 3,329 views
Movie Merger Madness - 279 replies and 2,492 views
That second thread bears reviving in The Game Room.
Garden Gnomes.
7 pages, 307 posts and 16,904 views.
Man I feel so proud 
Wow, I’d forgotten this one…it went to 306 replies.
Big bugs by a wide margin. If is wasn’t for that thread I would never have known about the horror that is the giant isopod…