For me Fate was a big shift. Aspects where such an eye opener for me but then Fate Accelerated came along and added approaches to the mix. Suddenly gaming shifted from what can your character do to how does your character do it. It’s sometimes a subtle difference but other times it’s monumental.

Another shift was probably WFRP 3rd edition. It was just an entirely different way to approach the medium of role playing. Physically turning rules and ideas into actual tangible components is fascinating to me. But it also added these variable resolution. No longer was the game a progression of pass/fail moments. You could pass or fail and have additional positive or negative aspects as part of the result as well.