Wing Commander. 'Nuff said. (Not 15 years, I know... Still, it stopped after 4 (1995) in my opinion, Prophecy and Arena are nothing more but spin-offs to my eyes.)
Random game thought :
Why is Bionic Commando Rearmed 2 getting so much hate? We finally get a real game and they're not even satisfied... I'm starting to hate the gaming community so f****** much...