Freelancer. Freelancer. FREELANCER.
Contols are nice,graphics are great,the skyboxes are STUNNING,and overall,a VERY good play. Then there's the Discovery mod for the game,which just adds a whole new level of awesome,if you play multiplayer...
And then there is a marverllous freeware game called Cave Story. I only picked it up a couple days ago,and get pwnt in Sacred Ground quite regularly,because I already used my Health Pot on the Red Demon,but that's not the point. The point is that the game is expertly crafted,with tight controls,great graphics for what appears to be a 16-bit game,the music is made of winsauce,and...It's just...Beautiful. It's free,and there's a translation out there (original is Japanese),so you have no excuse to not get it.
My two picks may not be as old as many of the other entries here,but they deserve mention. Amid a wave of the comparitive mediocrity of modern game releases,it's pleasing to see games of even that vintage stack up. Freelancer was released in 1999,with Cave Story (if TVTropes is to be believed) starting in 1999,releasing 2004,by one man. Not even ten years ago,these marvellous games were made. I only acquired them recently. They rocked my gaming world. And I can guarantee that they rocked others.