MGS3 Subsistence I would say is the peak of the series. The story was interesting but fairly easy to understand and the gameplay was fine tuned to near perfection (although inventory management was kind of a mess).
I would rank MGS1 over MGS2 just because of the characters, and I like Shadow Moses more than the Big Shell but both are pretty top notch games.
MGS V I would put up here, it's rather lacking in story but the gameplay is the best in the series and there's just so much replayability. If the game was a bit more fine tuned, I think it would easily rank over MGS1 and 2 but alas this is what we got.
Peacewalker I would put next, it's more like a mini-Phantom Pain but on the go. Good game nonetheless. Portable Ops would probably fit in here somewhere too.
I have to put MGS4 on the bottom of the Solid seires just because while the game itself was fun to play, the story was an absolute mess. Trying to wrap up an entire series such as this in one game is just insane. Despite it's flaws though, I still enjoy it a lot.
The MSX games are in a weird limbo for me, I haven't gotten to Metal Gear 2 yet but Metal Gear 1 I would probably put on the bottom. It feels clunky to play now a days but still a solid game despite the limitations.