On PC, the *absolute* best bang for your buck is the
Baldurs Gate 2 Collecters Edition , if you haven't played it. The problem being, most of us have
.
I spoke about it a bit in a strategy thread a while ago, but again,
Total Annihilation can still be found with expansion occasionaly irl and all over the net, and is probably just below
Starcraft (another great bargin, of course) in my book.
I second
Ico on ps2, although it isn't for everyone, and throw in The
Adventures of Cookies and Cream, if you're in a household with 2 gamers and don't need to shoot things to have fun. This is most assuredly one of the best hidden gems in modern gaming. I can't give the sheer fun of it and the originality of the concept enough props, and the closest I can think of to describe it might be to cross Toejam and Earl (genesis) with Crash Bandicoot.
Again with the not shooting theme,
Harvest Moon: Back to Nature, designed for ps1, is a wonderful bang for the buck.