It"s a fair point. WoW has done a good job at making long-lasting PvP content in the form of some good game types and lots of long-term gear rewards from PvP. But at the same time, if you count up man-hours of design and development, holy shit! How much more work have they done on PvE than PvP? Ten times as much? Fifteen times?
Frankly, I don"t understand why they don"t spend more time on PvP, because I think itis, at the very least, a significant portion of WoW"s appeal to levelcapped players. It took them two years to put in simple deathmatch arenas with a win/loss record, after spending a year and a half implementing some only very slightly innovative gametypes (other than AV, which was a genuinely cool, novel, and big PvP arena.)
You"d think they"d at least make some new goddamn maps for the arenas every month or two, huh?
EDIT: It"s true that WoW released with near-nonexistent raid content -- MC was such a shitty raid zone that it barely counts as content anyway. However, it still had a huge amount of very complete and polished solo and group content, complete with great scripted encounters, from 1-60. That"s as PvE as anything, and it was the main selling point at release. Better raids are a natural progression.