JK (more than Mots, which didn't live up to my expectations) because of the editability and replay value.
X-Wing Alliance for the same reasons plus that I've always wanted to be a combat pilot, but I don't have good enough vision.
*adjusts very thick glasses*
I just wish it was as easy to add ships to XWA as it is to add 3dos to JK/MotS.
"The Beasts know much that we do not." -Ancient Jedi proverb