Trick question: Which is the better movie, Spiderman or Ingmar Bergman's The Seventh Seal? Which is the better book, Harry Potter or Joyce's Ulysses? In both pairs the first is the low-brow, popular one, and the second is the high-brow, critically acclaimed one for a much smaller and more select audience. Terms like "good" and "bad" don't really apply, and you can't really compare.
I've had some complaints that I'm talking bad of raiding in WoW, but in effect raiding is the high-brow part of WoW for the smaller and select audience, while leveling up and doing quests from 1 to 70 is the low-brow, popular choice for the whole family. There is nothing inherently wrong with either. What *is* inherently wrong is having both in the same game and expecting people to switch from one to the other at some point. What if Spiderman 4 was an angst-ridden, existential movie that had Spiderman play chess against Death? What if the last Harry Potter had a chapter which consisted of somebodies unsorted thoughts in one endless sentence without punctuation? People would justifiably complain. Not because the high-brow part is "bad", but because of the bait and switch.
I think there would be room in the MMORPG market for a well-done game with forced grouping shortly after the newbie zones, leading up to more and more difficult content, and a raiding end-game in which only the best players could succeed. Unfortunately the last games that tried that weren't very polished, and just failed to excite. But as a concept, that kind of gameplay is totally valid, and is just waiting for somebody to implement it right.
But turning World of Warcraft into a game which is primarily about raiding is a mistake. You just can't make a game in which you can solo casually all the way up to 70 and then expect people to jump into a hardcore type of raiding where the slightest mistake wipes the whole raid. If your main game is for the average Joe, your end-game has to be too. If you want to have raids, you need to make them easy enough that a group of 25 average pickup players stands a chance. And you need to put in other sorts of things to do that are accessible to every age group and gender, for example player housing. It is not that WoW raiding is "bad", it just doesn't fit with the rest of the game.