Why is PartyPoker the biggest online poker site?

Party has been in business as long as any other site, and until recently did far more effective marketing than the other sites. This marketing attracts more people on the fringes of the game, ie "fish." Hence, more fish at party would be the main reason I can see to be there. I have not actually played on party yet, but was with Empire beofre the split, which I assume is pretty much the same level of competition. By the way, I suck, so don't listen to me.