I honestly think, from a purely gameplay perspective, there's very little that will ever top Ground Zeroes/The Phantom Pain. I think other games come close, but what they did with MGSV was something else.
The story on the other hand is, at best, disappointing. It literally goes nowhere and does nothing except answer a question from the MSX games that absolutely no one had asked or cared about.
I think, in many ways, it was a big answer to the cutscene critics but, in another way, it sort of lost a lot of what made the series fun, the ridiculous cutscnes and nonsense story. EDIT - It did have its moments though, the entire part leading up to and including "scatter your sorrow" scene.