So I got Dark Souls relatively recently and it has shot up to one of my favorite games ever. The atmoshpere, the combat, the secrets, the lore, the inevitable decline into madness and/or death, all of it is fucking amazing. I played through it once and thought it was damned good until I looked into the lore. Now everything makes sense and I fucking love it even more.
The PvP is broken due to unpredictable lag levels, but the game is still easily one of the best. Haven't played the second yet, have high hopes for the new game of Khorne the Bloodgod.
I love shit like what they did with the hollowing:
When you ragequit forever, that's you going hollow. The endless deaths got to you and you gave up. You're now one of the dead guys that you were killing before. That's why they made it as difficult as they did. That and to reinforce the feeling of inevitable death and decay. So meta, but in a good way I think. I was surprised to see that Expendables 3 did it too.

So what do you say? Have you recently found any games that have utterly blown you away from out of nowhere?