It's a series of games I never got into, sadly. They have such a loyal fanbase, must be doing something right. I think it was MGS5 that I tried to play, but spent like 40 minutes watching cutscenes in a plane on the way to the first mission. I just remember thinking that I'd have been better off watching a movie instead.

MGS 5 is a bad place to start. It's in the middle chronologically, and the last developed one, so it's relying on the player already knowing what came before and what comes after in the timeline. Without that knowledge it's just a really weird open world game. And since you mentioned "cutscenes in a plane" rather than "obnoxiously long hospital section" that would probably be Ground Zeros rather than Phantom Pain, which was really a demo with a very small open world. Or potentially you were playing 3, but it's hard to forget that that's "Snaaa-aake Eaateeerrr [External Link]."

MGS 1 is the best place to start. The narrative is tight, and it was the first Solid game released (there were 2 top down Metal Gear games before, but the parts of the plot that you might need to know are summarised within MGS 1) so it introduces the story and gameplay elements. MGS 3 is the second best place to start, since it's the first chronologically, and it has the best music and particularly good boss fights. If you want a chronological run (I'd strongly recommend a release-order run instead) it's 3, Peace Walker, Ground Zeros, Phantom Pain, 1, 2, 4.