By the time WoW came out, basically everyone I knew who had played EverQuest were really interested in jumping ship. EverQuest was dated, people were pissed at the direction the game had taken (more hardcore) and basically the game had begun to really strain and break under the weight of all the baggage of a billion expansions. There were whole classes that just didn't have a unique place in the game. Not even marginally unique. There were whole zones, whole continents, almost, that were just deserted. Not because people weren't playing, but because there were a dozen zones for the same level range and the old ones were uniformly worse, not fun, etc. WoW's launch was basically like what Warhammer or Age of Conan was for WoW PvPers, except that the game worked for more than 6 months.
WoW is doing something smart with cataclysm by removing a lot of baggage they've created for themselves and getting the game back to a more simple, core fun experience that has optional depth. This seems to be something they learned well from EverQuest's wanderings in the desert of shitty expansions after Velious. Major change now will piss some people off, but if designed with the right mix of fun, simplicity, and optional depth, it will probably set the stage for further dominance in the genre.