Well, I don't really want to get into some lengthy discussion about this (partly because I don't remember everything, it's been 7 years), but to summarise my view, I don't think the Solid Snake in MGS4 is an organic evolution of the character we see through the original Metal Gear through Metal Gear Solid 2. He has a pretty strong journey, but in MGS4, he's inconsistent. Not to mention him not being able to pull the trigger considering the consequences of those actions, which he knew to be real at the time, until the other guy comes and explains everything after he already decides not to pull it. It's basically the biggest way to piss on his character. He finds value in his life at the expense of others (as far as he knew), which is not Solid Snake.
It's been 7 years so my memory is fuzzy, but I hate that damn story because there was so much wrong with it in so many ways, and this is a series filled with crazy stuff.