Dark Forces was great. The only fault was the save system, but at least the enemies stayed dead if you died and still had lives left. But it made certain platforming sections very bothersome, losing one of your precious lives just because of a slightly mispositioned jump etc.
I also really liked the main villain, General Rom Mohc and the Dark Troopers were a menacing enemy, showing the Empire as the capable and menacing power it was supposed to be.
The series is also responsible for introducing one of my favorite Star Wars weapons - Stouker Concussion Rifle.
EDIT: It should also be noted Dark Forces 1 is banned in Germany for some strange reason. Have no idea why.
timppu: I recall I did play this game back when it was released, but it must have been some demo version because the starting level is not what I recall it to be (somehow I recall there should have been a "hologram" made of pixels of some planet or maybe it was the Death Star, rotating there on the first level...
The first mission is actually Kyle Katarn stealing the Death Star plans and handing them over to the rebellion. So yes, that was indeed the Death Star.