MGS 4 is... Weird. On one hand, it has some of the most entertaining levels of the franchise, but on the other, some of it's bosses are either mid or just a total slog to fight. In any way, it's a good farewell to the story of Solid Snake and a love letter to the entire franchise, specially for the first game. Be warned tho, some cutscenes are really long, so make sure you have a couple of free hours to play this game.