I play MGS for the story (or maybe I should say used to), not to feel like I'm a "badass" mercenary. I tend to scoff at people complaining about Raiden in MGS2 because of this. Their complaints are usually funny considering that Raiden is a representation of the player. Only thing is that Raiden grew out of his "whiny", rookie mentality whereas most players didn't. At least he did in that game. MGS4 basically pisses all over his character development of MGS2.
The problem with this is that people don't realize it was all part of MGS2's themes. Kojima had hoped that his audience would be smart enough to figure it out and not focus too much on the ending and it's questions. He himself said that he never planned on answering the questions that arose in MGS2 until he started receiving death threats. This was most likely a reason the answers in MGS4 are poorly done because it was never his intention to create the 4th game. I would've preferred the "cliffhanger" ending over a sequel that "wraps up" the series pretty horribly. Even then, like I mentioned before, it all seems moot as more games are being developed unnecessarily. Further complicating the storyline with retcons, new events, etc.
Being that MGS2 is a postmodern game, I felt that ending was good enough. I wouldn't have minded a sequel but as long as it wasn't a complete fanservice game like MGS4 was where "all" the questions were answered. Part of what is great about MGS2 is that it's theme hinges on the idea that it is a video game. Like I said, people seem to focus too much on two things to really pay attention to the themes:
1. Playing as Raiden
2. Unanswered questions
I still don't know why people obsess themselves so much over that.
Except that it isn't. What was so great about his death in MG2 was that it was ironic. Here we have the "greatest soldier of the 20th century" and he gets killed by his son with aerosol spray can and a lighter. It was fitting for a man who fell down from a hero to a egotistical, selfish, tyrannical bastard. Don't get me wrong, I loved Big Boss as a villain. If anything, he was my favorite character before MGS3.
In regards to Snake aging. I preferred it that way but only because I can't imagine people not wanting to play as him again if Kojima hadn't done it that way.