As far as the PC is concerned, there is only ONE GAME.
Star Wars: the Force Unleashed: Ultimate Sith Edition.
The patches that are out, are for that version.
It's only the consoles that have both versions of the game on the same platform (at least in the case of the PS3 and Xbox360).
All "Ultimate Sith Edition" is, is The Force Unleashed, with some bonus content added (Tatooine, Hoth, Jedi Temple, and a bunch of alternate player models and costumes). "USE" is an extended version of "TFU" then.
And TFU 2 is coming to PC as well as the other platforms. It's a new game, a sequel, based on the same engine, with some improvements (we're told).
The thing about PC games is that there are so many combinations of hardware and software possible, that it's a little tricky to predict. Sometimes though, games just aren't done efficiently and no system will run them very well (though usually over time, even games that are taxing on hardware will become playable, though not before the company has lost a lot of money from frustrated customers!).
TFU:USE apparently is very playable on what were considered "high end" machines when it came out (I'm talking on the PC of course).
The downside to all versions of this game is that the Framerate is supposed to be capped at 30 Frames per second. So even if you have the fastest computer known to man, you can't get any more FPS than 30. I'm sure people are looking for a way around it, but other games, like Star Wars Battlefront, stuck you with that until an official patch removed it.
But in theory it should be possible to have TFU:USE run as well on the PC as it does the Xbox 360 and PS3.