It's WoW but better, core wise anyways. Every mechanic and gameplay element is the same but better than WoW, but it failed to be different enough to steal enough of the casual fanbase to actually GO anywhere. Casual MMOs are social MMOs. Social MMOs sucks with no one to be social with. Not to mention it has an obvious lack of content due to WoW being ancient. Rift was pretty popular when it launched, but bombed pretty quickly thanks to shitty endgame content.
I'm curious to see how SWTOR works out in that regard. Since it's a game focused on PvE and social interaction, it's a hell of a lot more important to have "end game content" as opposed to a PvP MMO where you simply just hone your skill and perfect your builds. It better be packin' from the get-go or it'll lose some of its momentum.
Though it's still destined to do way better than Rift, solely based on its theme.