Star Wars is a great space opera. The original movies, regardless of whether they ripped off Akira Kurosawa or Battlestar Galactica, are as fresh today as the day they came out. The extended world works for people, as do the prequels to a certain extent. Single player video games have the potential to be awesome when set in the Star Wars universe, as evidenced by Knights of the Old Republic. They can also be pretty bad, as Force Unleashed 2 proved.
However, there are two major hurdles that any Star Wars MMO must overcome in order to be a successful when multiple people are involved, and both of these obstacles are inherent to the game world itself. I first experienced these when playing the old tabletop d6 RPG, and they will continue to be true even as Bioware releases a shinier version of the same concept.
1) Star Wars is a Dead World.
This means that anything that happened in the movies, books, or the extended storylines is unchangeable. If you decide you want to kill Darth Vader, or go out with Princess Leia, you are on your own. Anything set around the same time period as the movies must somehow adapt to that history, or it "doesn't count." This means that your character is bound by the vision of the developers, and the developers are bound by the vision of George Lucas, and even Lucas is bound by the layers and layers of history that have already been told about the Star Wars universe.
Anything not set around the time period of the original movies is fair game, however, which is why an MMO set either way before or after the movies could possibly work. However, this too is a gamble, as a developer has nothing in the game world to work with, since Luke, Leia, Darth Vader, etc...are either not born yet, or dead.
The Bioware MMO is taking that bet, by releasing a game set in the far past of the Star Wars universe, where they can make up whatever they want, with the downside that none of it has any relevance to the content we are used to. (For example, we can't go hang out with Han Solo.)
2) The Force Sucks
I'm sorry to say, it does. It's great for movies. It is absolutely horrible in a game.
Oh, they've been trying to spruce it up, make it flashy for the kiddies. They've been upping the ante on the Force, where at first it was really hard to chuck some rocks, while now Force users can jump around like rabbits or make people explode.
However, you've got this science fiction world, you don't have magic, or psionics, or mutations, or any cool alien races. Instead, you have two factions: dudes with lightsabers that are OMFGWTFBBQultrapowerful, and wimpy dudes with blasters. Like when Darth Vader pwns Han Solo without even trying.
Now that said, in a game they can easily tweak it so that lightsaber characters are as strong as blaster characters, but that is not entirely the point. Force users get all sorts of neat abilities that non-Force users don't get. What do the normal people of the world gain in exchange? Yay, they can repair a droid, use a jetpack, or ride a tauntaun. Woo.
The Force is further limited by #1 above, because the game developers can't let it do anything. They can't let you shoot fireballs, summon monsters, teleport, time travel, go invisible, or one of the many, many things that you haven't seen in the movies that don't fit the "vision" of the world.
Not to mention that any discussion of the Force is inherently linked to the morality of the Force, because that's the way the game world is set up. Like you can't use Force lightning without being a bad guy, because that is a bad guy power. Even though hacking people in half with a laser sword is just fine. I mean, you've got a bunch of so-called good people that can't be emotional at all, can't have sex, can't have relationships, and there are plenty of those dudes running around. Then you have the evil dudes, who constantly let their desires run rampant, and none of them got it on with a hot Twi'lek? Right.
In short, everyone wants to play a kickass Jedi/Sith with awesome powers and a lightsaber, and nobody wants to play a second-class normal person. You've got a crappy source of "magic" with crappy rules attached to it, in a dead world where everything neat has already happened, and your character plays second fiddle to the NPCs, and you play third fiddle to other players if you happen to play a non-Force character.