KOCollins: My Favorite old(er) games to play that I keep playing that GOG doesn't have (yet) are:
Freelancer, Darklands, Rome Total War, Knights of Honor, Heroes Chronicles, Morrowind, Civilization 2, Diablo, Star Trek a Final Unity, Siege of Avalon
I could go on, sorry, I just couldn't put one down. Most recent install would be Freelancer and would be right now(this thread has convinced another install outta me)! I never get tired of playing that game...Once I install it on a computer it stays on till said computer is fried and buried. I mean with 500 GB you just have to fill it up with game goodness don't you?
Rome Total War was epic in design and delivery, with a great score to set the mood as you progressed. It is one of the games I installed, kept on, and revisited as each faction.
Recently found an extensive/professional mod, Roma Surrectum II, that I was quite impressed with. Simply copied/pasted my whole RTW directory structure to a clone grouping, installed the mod, and played away. Was quite impressed by all of the additional units and factions much more representative of tribes within regions such as Gaul and Germanica.
Edit for typo.