Even years afterward this is still a great game.
When this game first came out I was amazed at the scope, the game just feels big. Well more than ten years after this game was released I still get that feeling of granger everytime I pop it in. The levels are big, even by today's standards, there are plenty of hours of game play here. If you just play through without taking your time to take in your surroundings it will probably take you ten to twelve hours. But you'll really want to take you time and get a good look at the world around you. Even with the technical efficients of great next gen games such as Halo or Call of Duty 4 this game still stands above them in the immersive feel that you get from it.
The story is pretty stock but the two available endings, which you see is determined by whether you are on the dark side or the light, give you a good sense of closure and you will definitely want to play through at least twice to see both endings.
There is also a good deal of replay value to this game. The single player game is immersive enough that you'll want to play through it several times to see the different endings or just to see everything again. There is also a great multi player mode. While not as grand in scale as the single player game it is still very entertaining. You have all the standard modes: Free for all, Capture the flag, Team Free For All, etc. And while you get all the same weapons that you do in the single player game you'll probably spend most of you time dueling it out with light sabers.
Even though this game is pretty old by now the last time I was on I still had no trouble getting into a game with several people in it.
In conclusion, this is a great game. If you've never played Jedi Knight: Dark Forces II or if you're a seasoned vetrine you will find a great deal to occupy your time with. And if you can look past the out dated graphics then this is a refreshing break from modern FPS games.