The first M game that I "officially" bought and played myself was Resistance: Fall of Man, age 11 or 12. Initially I was nervous of playing an "M" game as I was afraid of the violence at the time (hey, I was a pansy then!), but my dad told me that I could buy whatever game I want "so long as you don't take it too seriously".
So, yeah, been gaming with many-a-M game since.