I really liked MGS4, I think it gets way too much shit, I've actually been replaying it at the moment as well. Sure there are a tonne of cutscenes, but this is the one that's really meant to tie up everything in Solid Snake's storyline. After all the shit they've accumulated over the years, It pretty much had to happen.
The actual gameplay is smooth as butter, it's got the most expansive CQC in the franchise and there's so many little details just with how you play that make it feel like a game that was really built with care.
Yes there are a lot of issues - Nanomachines end up being the solution to too many problems, Drebin and his monkey are ridiculous and the last chapter consists of one sneaking section, 2 boss fights, a corridor and more than an hour of cutscenes. But I still think it's a great game.
The first 2 chapters give you different options with how to tackle the stages, with branching paths and the option to fight alongside the rebels. Chapter 4 is a great bit of fan service and actually a really fun chapter of the game. How could any MGS fan not be excited to revisit
on that Chapter. It was all really thoughtfully done.
Chapter 3 is probably the biggest shit-stain on the game as far as I'm concerned. I understand that was designed by someone different (The director of NeverDead if I'm not mistaken). Just a really terrible, slow chapter that is absolutely zero fun to replay.
People bash it because it's got more cutscenes than gameplay, but as I was saying this was meant to tie up just about everything and it's just a clean cut way of doing it. Sure they could maybe have edited it down a bit but I don't think with MGS you should separate the cutscenes and the gameplay too much - they're all part of one package that makes up MGS. It's a part of what MGS is.
Basically - great game, some problems but mostly just given too much stick.
MGS3 is (in my opinion) the best MGS all round, but 4 had the best gameplay of the series... until it was dethroned by MGS V.