Just that. The earliest game you keep around and play (more or less) regularly. I'm simply curious.
My own is Hidden Agenda, from 1988. I reviewed it for a magazine when it first came out, enjoyed it thoroughly, and have played it since then. Not all the time, but it still works very well, and nobody has followed up on its way of handling things.
After that, Darklands, from 1992. A game that amazingly enough hasn't been redone, though I suspect the current rights owners' attitude towards remaking games probably accounts for that.
Over to you. Just please, refrain from stating something like "1988!!?! Wow, I wasn't even born then," because I at that point I will have to purchase a steel cane with a depleted titanium core and shove it where the moon don't shine. Thank you. 
