What's the longest time between starting a game and finishing?

[maniacalpha1-1]

I think I played the Serious Sam's demo back in 2001 and I just finished the HD 1st and 2nd encounters in the past week, having gotten them for like $10 on sale this year. I also started Arcanum: Of Steamworks and Magick Obscura in 2001 and I may never finish it or even get past the first city, lol.

BTW, is Serious Sam 2 even on Steam? I can't find it, waiting for price drops to get Serious Sam 3.