Both are great fun and among my favorite SW games, but Jedi Outcast is better. It's a "bigger" story, it feels more cohesive and more like it belongs with the movies. Academy feels more like a young adult spin-off. It's a lot of fun, it has some great levels, but it's very episodic, the stakes never seem high, the protagonist is a blank slate with none of Katarn's charm. But it serves as a good post-script to the series. I like leaving Kyle as a master and a teacher right beside Luke (the real, pre-Disney Luke).
Jedi Knight is great as a shooter (and has fantastic level design, imo superior to Jedi Outcast/Academy), but the lightsaber combat in it is pretty atrocious tbh.
Yeah, I really loved it - the levels, the FMV cut scenes, the story (such as it is), but I barely used the lightsabre outside of the duels. The improvement between JD and JD2 on that score is absolutely astounding.
Still, to be absolutely honest, while I'm glad I played through the whole series, I think I'll only ever go back to Jedi Knight II and Academy. They are just much easier to get into.