The X-Wing series was brilliant, but convincing them to run on modern PCs is quite the task. DOSbox is capable of doing so but I wouldn't expect fantastic performance unless you set the game's detail options to their lowest settings — my 386 ran the games better!
I should have mentioned it above, but I've had quite a bit of fun with the Half-Life 2 mod Eternal Silence. Think of it as something like Battlefield 2142's Titan mode except in space and with a great deal of emphasis upon fighter combat. The game is simply a blast and could certainly use more players.
Supposedly all that you require to run it is the Source SDK Base, which can be downloaded through Steam. I'm not sure if you're required to actually own a Source Engine game to do so, though.
You could always pick up Team Fortress 2 if you find yourself lacking.