Ok, why is KOTOR better?
1. It takes about 17 hours to complete if you already know where to go but still want to do most of the side quests. ROTS is only 2 and a half hours.
2. You control the characters, storyline, and what happens in KOTOR. You influence it, your characters, your characters' strengths and weaknesses, even what Revan looks like. In ROTS you simply have to watch someone else's vision, which will usually lead to a few disappointments to people.
3. It's much more fun to control what happens, light or dark, who you fight, and actually fighting knowing just how powerful you are and constantly growing stronger with each enemy you kill rather than watching someone fight, staying at the same strength throughout the whole movie.
4. KOTOR gives you a sense of galactic importance, like the fate of the galaxy rests in YOUR hands, while watching ROTS you simply get the feeling that Anakin has his own galactic importance but it doesn't relate to you.
5. ROTS has very few things people didn't already know, and those things only gave a slight shock when it happened. KOTOR on the other hand, you don't know what's going to happen, like the major surprise, getting captured by the Leviathan, Bastila turning to the dark side (ok that was obvious) but again it also comes down to you choosing what to say at every moment, whether to be a smart ass, nice guy, or bad ass and choosing which side of the Force to be on.
6. The freedom to do whatever you want. If you want to see more of Tatooine you can, or talk to someone else, or learn more about your companions, your lightsaber color, etc. but in ROTS if you wanted to see a little more of Coruscant, know more about this character, etc. it's just too bad.
So that's why I think KOTOR is better than ROTS.