That will be KOTOR 2, Jedi Academy, Battlefront 2 in rough order. I can enjoy others but these are the ones I'm likely to actually come back for.
KOTOR 2 for story, but I wouldn't play again without the restored content mod as it is noticeably unfinished in vanilla. Apparently the company that made ports to other platforms also made some under the hood improvements. Hopefully the two pair up nicely and make a better experience then I remember. You'll notice it tops the list but I don't play it often. It's one of those games I feel I can only get the most out of once, maybe a couple more times. I play a certain way and that is the canon way of it for me, I'm not the type to play every which way with minute differences again and again.
Jedi Academy I play because mods good. End of story, check out moddb. Or Galactic Legacy in particular...
Battlefront 2 should still have a halfway functioning multiplayer community, and is a fun game anyway to give a shot.
Various old star wars games are available in fairly cheap bundles, there's
one for under 30 bucks on Steam that gets you a bucket of neat Jedi Knight related games including Jedi Academy and Outcast, which is a nice one for story. In general the old ones aren't bad for the wallet to pick up and can pack quite a punch for gameplay.
I've heard good things about Republic Commando and Dark Forces but I have no experience of them. I do know Dark Forces is best served under The Force Engine which makes it run properly on newer systems.