I enjoy 'Mad Dog Mean' modules. I enjoy their challenge and the lethality keep me at my peak.
Tomb of Horror - Loved this one. Of course, I was the only character who didn't die.
Labyrinth of Madness - Oh, my.... Our party lost 3 out of 6 characters before we even got into the labyrinth proper. Again, I enjoyed very much (I was the only one who didn't die at least once)
Return to the Tomb of Horror - (how many ways to die, let me count the ways...) Only original character that survived yet again. Again, I enjoyed.
Heart of Nightfang Spire - not quite on par with the above, but still fun. Several people survived this one, but not all
Bastion of Broken Souls - oh, my god. The opening encounter really sets the tone. The Bastion itself is killer, particularly the energons. I was the only one to walk away with an original character who didn't die from this one.
RttToEE - Nasty. The body count was high and the other players went through the motions of creating characters. This was the adventure that I realized that the only person having fun was me. I had a character who didn't die. Each other player had 2-3 character each.
That is when it struck me - I was having a great time, but I now wonder about the other players who had to create new characters or who had their characters raised several time. None of my fellow players complained, but RttToEE was the first time I noticed the other players were just going through the motions after they had lost their characters for the second time.
I may be weird but I like the challenge of 'living on the edge'. So far, I've 'come up spades' in every adventure, which might be the appeal for me.
Maybe 'survival = fun' for the Mad Dog Mean modules. If you survived, it was fun. If you are on character No. 3 for that adventure, I can see where the adventure would lose its luster.
Still, I like the high bar these adventures set.