Outside the MMO, Earth & Beyond, cancelled way before its time, I have a hard time naming any space game that so effectively captures the wonder, mystery, and fear of space travel as Freelancer.

I remember cruising through a desolate system brimming with the broken hulks of battlecruisers to be ambushed by alien Nomads as I tried to beat a hasty retreat with my cargo bay full of high-grade weapons salvage.

Yes, and so easy to mod. The cancelation of the sequel broke my heart.