Wait, WHAAAAAAAAAAT?? I-War is on GOG??? Oh, [insert deity], it's true! There is justice in the world. (Translate: I-War is awesome through and through. However, it's probably the most difficult game I've ever played. I think I could finish the training missions without invulnerability, but...)
I don't really go there very often (just went there to check up, and found that I suddenly had Ultima IV in my library, waiting to be downloaded - k, thx, not that I ordered it), but I can vouch for the quality of nearly all of their D&D-titles, if CRPG is your cup o' tea. Dark Reign is also the first and only strategy game I ever liked (1, not 2!) - can't say I know why, but it does seem to have brought some technical innovation to the RTS-meme. The story is, I suppose, not the main attraction.
I think the Myst and Uru games have their appeal, but Uru is perhaps just about to take off - Cyan fairly recently went official with their plans to opensource Uru. Perhaps a VERY niche series.
Also consider staying well away from Syberia. I suppose they're solid adventure games, as the games themselves go, but the stories are just... w3rd. Cute tales of misfits/outcasts/outsiders/progressives looking for a purpose in life, I suppose, but... w3rd. Weirder... W333333333RD!