Unfortunately from what I know there is not another game in the Jedi Knight series... Outcast was my favorite though, if you have not played Jedi Outcast I really suggest trying it.
People suggested Elite Force 1-2 and Deus Ex over the net. Elite Force 1-2 -> I may agree regarding the first 2 Dark Forces games, not Jedi Academy though.
Deus Ex - Customization is awesome, game is an all time classic. But I am not so sure about Jedi Academy resemblence.
Jedi Academy is still my favorite game of all time that has lightsabers. Everything since might have prettier graphics, but nothing else has come close to the feeling of direct control you get with Jedi Academy.
The biggest problem I had with Jedi Academy was that blocking Blaster Bolts was a passive skill. Even at the 3rd level (highest) of that skill, you still can get mauled by a single Imperial Officer (which only carry pistols. PISTOLS). What's up with that?! Would've liked it to be more of an active move to block stuff. Also the inability to defend against charged Disrupter Rifles shots (at least in SP) was a downer.
But despite all these, I did love Jedi Academy. Might try Jedi Outcast, since several people here recommend it, ya.
If you haven't already, even though they are passive in means of combat, you can go for Kotor 1 and 2. The storyline and characters are quite fun there.
mmmm this brings back frond memories, like my horned chick in black lingerie and double-bladed red light sabre which turned to the dark side at the end. (well actually, she was plannign it all along). Oh yeah... on topic... no, I don't know of a successor.