One of the GOATS, there really isn’t anything like it. And even its weaknesses are strengths, which is a rare thing. The story doesn’t rail-road you much, so it leaves space for your own story instead, which makes it much more engaging. The engine allows you to cheese many things, so it becomes a point of honor to make runs where you don’t cheese, and don’t exploit broken mechanics, and so on.

Also playing the games with a party is an experience, but solo’ing is something completely different on its own that you have to experience.