I have all Commander Keen Episodes from ID on original floppy discs^^ They are the first games I played. After I finished all of them I start playing The last Dynasty from Sierra. Retro rules!
The oldest game I own, would be Oni or TES3: Morrowind. I don't the dates apart from them games. Oldest PC game I have played is TES1. Its free to download and it plays just great with DOSBox
Many games from that age looks better than some today. Though that's more to do with art style than the technical aspects. Oldest I've got is Akalabeth, originally released in 1979.
I have a lot of old games, such as: Commander Keen 1, 2, 4, 5, & 6 The Amazing Spiderman Prince of Persia etc.
The D&D program from 1991 on an old IBM floppy. Still plays perfect! I also own the original cassette port of spacewar, from 1985. It's a little beat up. I got it from a book-sale. Oh yeah, and I own the Apple II game: Adventure, from the mid-1980's. Also a cassette. This is technically a Mac game, but most computers were the same back then, so it's a PC game.
Haha the Oldest game i got is F.E.A.R I gave away my older games though i think i might have StarCraft somewhere ima have to find it