KOTOR is fun and the twist is great, but it's far from perfect. The Sith don't feel evil, they act like high-school bullies. And most characters are pretty bland (well, there HK of course. But Carth or Bastila never seemed interesting to me, and Bastila turning to the dark side came out of nowhere)
KOTOR 2 is just a lot more interesting, and has the better characters (not even just Kreia. Atton or Visas, too. And the Sith Lords may be pretty OP, but they're OP in a really fascinating way that relates to their character)