gets around the occasional frustrating mission or boss fight by having probably the most engaging gameplay loop in a metal gear game that isn't MGS2. the mission-based and base-building style gameplay of capturing soldiers to hire them as combatants or R&D members (among other roles) for MSF fits big boss' leadership qualities more than it does solid snake and is engaging in its own right
they didn't really need to continue big boss' story after MGS3 since I think the end of that game already made his motivations for his more cynical point-of-view in MG2 - but peace walker manages to make its story worthwhile by showing him struggling to come to grips with the boss' death and having him slowly develop into his more villainous personality from MG1 and 2 by the end of the game
the best part, however? this game is deeply unserious - moreso than any metal gear game before it. and I kinda love it for that. the comedic briefing tapes substituting for the prior games' codec banter and the various wacky extra ops that see BB doing silly shit like playing pooyan with fultoned soldiers, or going having rough gay sex with miller under a cardboard box. we've come a long way from bisexual vampires