KotOR: The best. Because it was so original and cool, even though it's based on the earlier Tales of the Jedi comic (my favorite comics ever) it did it's own thing, and the fact that we are still here talking about it over a decade later is a testament to that
I think Bioware taking a best selling game so far from the source material (time-line) opened the gate for the rest of licensing to push for something other than Original trilogy centric products, and made the EU much more legitimate than the Novels ever could. (as a side note my other favorite comic ever, is called shadows and Light
from a Dark Horse Star Wars: Tales #23. It's a fully realised story of the exploits of Duron Qel-Droma and his counterparts that you read about on the Datapad you find in the cave on Korriban (ignore the front cover of the comic, thats one of the other stories in issue) check it out)
The Old Republic: I have several 55's, but there is still something missing for me, it doesn't give me the same feelings KotOR, SWG, JK and TFU did.