Blizzard's RTS's weren't that great, theres no fun about conquering a map with forty men for no reason. TW series is so much better.
Yeah - that's pretty much what all RTS games are but Blizzard's RTS games had something about them that attracted so many people. They were fun, had great characters, and had even better stories and plot lines, etc
MMORPGs still have stories and plot lines.... my one friend loves to tell me Warcraft Lore whenever I ask him something about the game.... but I think it's the idea of building a character from scratch and watching it grow through hard work that attracts people... and if you can continue to grow, you'll continue to play... it's that simple