My oldest would have been Horace and the Spiders and Harrier Attack on the ZX Spectrum. Think I got them around 1982-1983. Thats if you don't count Grandstand console games (with lightgun that looked like an awesome SWAT type gun) and things like that.
Unfortuantly my parents gave it all away (inc. about 3 computers) to charity
Without telling me
I know, I know... Anyways that leaves me with (quick check)...
A few games on the PC from 1994 (I can't find Doom or the like anymore...). The earliest of which is... Descent I believe. Good game that. Someone remake it now!...
Ooh, ang on found salvaged stash of ST games my parents didn't throw out. Nah, can't be bothered... Make that something like 1989.
Cheers
I am 99% probably lying in bed right now... so don't blame me for crappy typing
Current fave quote : "She was like a candle in the wind.... unreliable...."