Best PC Game?

This is a complex question to answer in my opinion XD. A game might be extremely fun to play when you start playing it, but then after you've spent hours and hours playing it, it will eventually become boring. So now if you compare that old game to a brand new game, you might think the brand new game to be more fun to play (and thus a 'better' game). Also, if there is a new game that is very similar to that old game, but is slightly better, you might still find that new game boring, because you've already played a similar game to it and thus you won't enjoy the new game as much and won't rate it that well, even though the new game is actually better. An example would be the Pokemon games: you might have enjoyed the Red/Blue versions and rated it very very highly, then you might play Gold/Silver and not enjoy it as much as Red/Blue since it's a very similar game and you won't be as excited about it.

Anyway, rating a game in terms of the amount of time I spent where I actually had fun playing the game (i.e. the game which I spent the most amount of time actually having fun on), I would have to say that it's Runescape. Even though other games I really really enjoyed, like Skyrim, Subnautica, Witcher 3, etc. I got bored of those games within a few weeks, whereas with Runescape it took me many years before I got bored of it.