I don't even think I've played 20 games, at least I don't remember that many well enough to rank them all.
This.
Nobody said anything about ranking, he's just listing his top 50 games (in no particular order, I assume).
I've played more than 50 games in my life but most so long ago I don't remember them that well. As for which games get on the list, with such a long list, usually it will be highly correlated with whatever games you happen to have played and moderately enjoyed at some point in your life, and not necessarily with any inherent value in the actual games.