Never. And I'm 100% okay with that.
I constantly add games to the backlog and replay games I've already beat. Even if I live for another 40 years and am able to beat 60 games on average a year (40 x 60 = 2400 games beat), I'll still have games I've yet to play. However, I don't see this as some sort of failure or act of futility, but rather an opportunity to play as many games as I can in my relatively short time on this planet. Even if there are games I never get to, I'd rather think of all the ones I did play, good or bad. Obviously, I prioritize games that I think I'll like more or ones that are widely considered good games. I've also become more okay with dropping a game if I don't like it, especially if it's a longer game (10+ hours). If I do live to be 80, I hope i get to look back and smile at all the amazing gaming experiences I had throughout my life.