It's a simple thing to say, but Freespace 2 truly is the best game of its genre. There hasn't been a space combat sim since that's truly captured the atmosphere and epic scale of the combat. The gameplay model is just the right side of "simulation" to give it some real depth, whilst being accessible to newcomers, and for once, your wingmen are actually useful (giving your wingmen orders is ESSENTIAL in order to be able to survive the later missions). The combat is fast paced but deliberate, with much thought to be given to the overall situation if you're going to complete your objectives. There's nothing quite like dogfighting in-between two MASSIVE capital ships, dodging the exchanging broadsides of beam cannon fire and flak bursts whilst trying to get a lock on your enemy. It can be a pretty heady experience.
It's a real shame that the genre has since died out (although may be on the verge of a resurgence given the number of space combat sims coming out of Russia at the moment). For the time being though, this decade old game, combined with the graphical updates from the Source Code Project, will more than see you through your desire for one more space combat game. A classic that's definitely stood the test of time.
Hit your burners pilot!