KOTOR 1 is hard to beat, but KOTOR 2 seems to do a good job is building upon the first game. Making a lot of QoL improvements in the process. I'm not super grabbed by the story yet, it feels like it's unfolding very slowly but I think it's a very strong game nonetheless.
I love KOTOR. It stands out as one of the best games that's ever been made. It takes the star wars universe and turns it into a living, breathing world completely standalone from the movie franchise. Super immersive as well.