I remember that my nephews, who I taught how to play Smash (they love it), grew interested in Snake because he was "cool". This was back in 2009, when they were both younger than 10. They also ask me a bunch of questions about him that I have to look up to answer.
Would I let them play a Metal Gear game today? ...Probably not. They have both seen worse through movies, but the older one, who is IMO old enough to at least test it out, is
very analytical about things and psychologically serious to the point that I fear it may bother him on an emotional level.
The younger one, I feel would have a blast, but not quite sure I would feel comfortable with him playing it
just yet.