MGS V is my most played game of this Generation bar none. The gameplay loop is fantastic, the story is epic (though it isn't perfect, and falls off in the final stages because Konami shat all over Kojima's dreams), and I think that the key consideration to be noted here is that it is probably more original than Zelda. Zelda's stories are oftentimes forgettable garnish to the action, so I'm not sure that's enough to take it over MGSV.
Not trying to put down Zelda but it is a decades old series, and it did make a shift to open world a la Skyrim etc. This has all been done before. MGS V itself also did the open world shift - but it did it in such a novel way.
We're deep into the competition, and this is a semi final, both of these games are hugely accessible and entertaining (unlike the balance in the previous poll, arguably), but I'm going with MGSV because it was a one-off, it was hugely long and entertaining, and the gameplay was pitch perfect. But Zelda should get votes because it is hugely successful and accessible, portable, and highly regarded.
I can't even begin to guess which of MGSV and Witcher 3 I'd vote for in the final poll...
On the other hand
It'll be the hipster *shit combat* brigade for W3 vs the degradable weapons brigade for Zelda xP