KotOR
+ Strongly defined, archetypal characters. This can be a problem when done poorly. I thought KotOR was an example of doing it right. The exceptions were T3-M4 who had no personality until KotOR2, and Jolee Bindo whose personality and sidequest broke away from the strict confines everyone else was operating under. He could have easily fit into KotOR2.
+ Capturing the classic Star Wars feel. KotOR was IMO the best Star Wars related product for years following its release. It didn't try to be edgy or clever. It was a straightforward tale about heroes being heroic and saving the day at the end. KotOR also immersed me into its world in a way that felt like my character was a part of it; rather than an avatar in a power fantasy fanfic. Well, at least until the Star Forge. Got a little ridiculous there. 
+ Flashy combat with D20 underpinnings. I'm biased here being a fan of D20 rules.
Despite there only being six classes, there was a fair bit of build variety as every Revan was multiclassed by default and there weren't too many garbage feats. Trying different builds alone carried me through over ten playthroughs. KotOR was the first Star Wars game I played where it felt like my character was actually a Jedi badass, and not a moron swinging around a lightsaber like a 2x4.
- Horrible good and evil split. You could either be a lawful good paladin or a chaotic evil psychopath. There was precious little nuance. Jolee Bindo's personal quest stood out precisely because of how black and white KotOR was.
- Zero challenge. It was very easy to build a walking deity if you knew how. Going into it with knowledge of the D20 system, I had a very easy time creating a Revan that was unstoppable. Who needs a party when a Scoundrel/Jedi Guardian can force wave or stasis field a crowd then go on a sneak attacking flurry spree?
- Useless skills. You needed persuade. If you wanted to hear all of HK-47's stories, you needed some repair as well. That's it. Mines could be fun--particularly if you focused on blasters instead of lightsabers, but hardly necessary. Most skills were simply too unrewarding to feel worthwhile. More so if you ran around with Mission or T3-M4.
KotOR2
+ KotOR2's plot was an interesting take on Star Wars mythos. Love it or hate it, it at least tried to do something different with the usual light versus dark dichotomy.
+ Interesting and varied party members. KotOR2's cast was a lot less cookie cutter in concept. Even characters that initially seem easy to peg might surprise you once you dig into who they are and how they see the world around them. That does not apply to everyone, but it does apply to most of them. I particularly enjoyed the dynamic between Kreia and The Exile. Putting aside all the debate surrounding Kreia's motives and characterization, one thing made a bigger impression on me than any of that. Simply, the mentor/protege relationship those two had going.
In many RPGs your character is an unstoppable, unflappable badass who is rarely questioned by anyone in their core group until a specific quest or an endgame binary decision forces conflict. Kreia was a foil that frequently challenged the player to examine their decisions and the reasoning behind them. She was a true companion on your character's journey--not a follower who occasionally helped you kill stuff.
+ KotOR2 did a better job of making skills relevant than its predecessor. Just having persuade didn't cut it anymore. Not if you wanted to see everything and overcome every challenge.
- The story was a disjointed mess at times. A lot of it did not make sense my first time through. I was expecting a plot akin to other Star Wars stories and instead had to spend time reading between lines and piecing concepts together. It was not until my second playthrough I truly *understood* what KotOR2 was about. The endgame in particular was a rancid, rotting mess. I know there is a cut content mod out there now, but judging KotOR2 as the product we actually got, I consider its story a failure in terms of execution. It is a tale worth experiencing, but it is by no means a flawless masterwork.
- Even easier than KotOR. I felt the new prestige classes were poorly balanced, and in some cases, completely broke combat into a snooze fest.
- Party homogenization. Nearly everyone becomes your Jedi or Sith student. Flashy blades for everyone!
Sigh. It sucked a lot of what makes putting together parties interesting in the first place. The temptation to go that route with most of your party was high too. Jedi were OP in combat, and from a storytelling perspective the narrative felt like it pushed the player into that direction.
- Poor area design. Either as a result of cut content or aesthetically speaking. KotOR2 was an uglier game than its predecessor; which I suppose fit its theme but still made it less interesting to look at. I still remember my disappointment when returning to Dantooine and seeing all the life sucked from it.
KotOR 3...000!
I'm done with KotOR. The official canon for both games drove nails into its dessicated corpse. Somehow they ruined Revan *and* The Exile for me in one fell swoop. They could release a new game and call it KotOR, but the less it has to do with the first two games and SWtOR the happier I will be. Start fresh with new ideas and try not to ruin a good thing this time.
Not constructive, I admit, but it is what it is.