>the OT or PT.
Kotor 1 was already nearly done when Attack of the clones came out, so it couldn't rip that off, or Revenge of the Sith. It did rip off Phantom Menace heavily, as seen in >Revan
what about Revan is original? He's just a generic Sith Lord. Kotor 1 never explains why Revan fell to the darkside. The plot in Kotor 1 is literally "Revan and Malak wake up one day and decide they want to betray the Jedi, conquer the galaxy and murder billions of people for fun". The game never even hints at any underlying motivation for them to do this. That only happens in Kotor 2.
>the star forge's backstory, the Rakutans
I'll grant you it's original (the only original aspect of Kotor 1), but it's also fucking retarded. Literally the dumbest shit anyone ever came up with in the EU, and that's saying a lot considering all the dumb shit in the EU. The idea that these goofy lizardmen are this ancient precursor race that are the most powerful race that ever existed, the oldest wielders of the Force and basically created the star wars universe as we know it makes it impossible to take the setting seriously.
The whole ancient protospecies thing feels very antithetical to Star Wars. Having one group responsible for creating all intelligent life in the galaxy just serves to shrink the setting down, reducing its scope and scale, which is the opposite of what a good Star Wars story should do. (Honestly it's more Star Trek, if anything.)
Much of what makes Star Wars work is that the world-building hints about so much more than what can be reasonably detailed. For example the cantina scene in the original film, filled with all sorts of unique and weird aliens. That helps sell the idea that there's this huge universe that extends outside the frame we are watching.
KOTOR2 gets this right, its plot suggesting there's an ancient, mysterious empire located outside of known space.