Ground Zeroes is one of the greatest prologue chapters in gaming history, it's an absolutely perfect introduction to The Phantom Pain.
Speaking about TPP, its gameplay is one of the most fun experiences I've had in a game in a very long time, probably the best in the MGS series. The story is obviously the weak part of the game but unlike many others I think it has its good moments and also I didn't really mind the concept of listening to the audio tapes, some were actually really good (especially the ones you get after beating the game).
Overall despite the lack of KoTF (the infamous mission 51) I have a very positive opinion of this game, I still play it from time to time

I understand now why Kojima is so insistent that MGSV isn't actually "5". This is clearly the culmination of the series, the final and total statement after which anything else is just an elaboration on an existing theme. MGS4 is so thoroughly and maddeningly crafted from hundreds of layers of metanarrative, it almost doesn't matter that the actual play you do is only barely present within. All previous Metals Gear Solid were in a sense sequences of set pieces that blended the gap between play and cinema, so it makes sense that this goes hardest of all on the overlap. All the cutscenes are playable, and all the moments of play are just moments between cutscenes.

This isn't a complaint, by any stretch of the imagination. Without any shred of irony, I'll say I consider Kojima an auteur and this game a masterpiece. From the opening, where you flip through FMV channels including David Hayter being fictionally interviewed as David Hayter, it sets out to reproduce, parody, and critique a whole world of information technology and the culture produced by it. And somehow it succeeds! This one relatively short game embeds within itself all the manic violence on the battlefield of thought that the characterizes the 20th century. Even its labyrinthine plot with double-cross atop double-cross serves as a mirror of the care and attention that must be paid to understand the complexities of our own world.

As a cinematic experience, I prefer Metal Gear Solid 3. In terms of raw fun of play, I'll always pick Metal Gear Solid V. But as an art object, it's hard to imagine a game more complete in itself or absurdly competent in its work than Metal Gear Solid 4.