I believe that Freespace 2 is the best space-sim series, and one of the best games ever made. While Freelancer had many good qualities too, I believe nothing can beat the epicness of what Freespace 2 achieves. With the SCP upgrade, around 300 vessels now are allowed to be in the game at once, giving many more options for mod development and amazing missions. I'm experimenting and playing with the editor to create good quality battles, but it's definitely not hard to pick up, but hard to master. ;)
If anything's worth your 6 bucks, it's this game.
- JC