I’ve always played video games one way or another, so I consider them all to be life changing. In a general sense, because getting games in my country wasn’t easy in the 80’s and 90’s, and most would bring them from the US, so I learned English through the games, which opened the possibility to hang out (online) with people from around the world.
But I think there’s two games that marked me:
Vampire the Masquerade Redemption, because until then I hadn’t played any story-driven true RPG. And after I finished it, I moved on to games like Fallout and Dragon Age, which led me to learn about modding, communities, etc.
The Last of Us, because until then no game (no matter how much I loved it) made me feel so intensely. I played it in several days, and each day I was emotionally exhausted. The ending left me speechless. I would wake up every day feeling like I’d been hit by a truck, for about a week or two.