When I was about 2 or 3 I used to play the most basic PC game. It was on a beast of a floppy disk and involved getting a bear some birthday cake. And pushing a button.
I guess I 'properly' started gaming at age 4 or 5 when my parents bought me a gameboy colour for my birthday along with Pokemon Red and Blue. Or at least, I think that's when I started.
Consolewise was a few years later when the Gamecube came out which remains to date the only console I've got that I didn't wait a year for the price to drop on. Admittedly this was a joint Christmas gift for my sisters and I but y'know...
When it comes to my platform of choice, I didn't start proper PC gaming for quite a while. Probably not til around 2004, and even that was relatively basic stuff, no Shooters or anything. In fact, around then I think all I played was Strategy. But as I led up to that I'd sit and watch my dad playing all sorts, mostly FPS, and I'd be his wingman, pointing out enemies he'd miss, memorising where there were hidden health kits and other such irritating back-seat driving playing techniques. I still sometimes watch, just 'cause it's one of the nicest ways we spend time together.
Wait, that makes it sound like we hate each other or something XD It's not like that, we just get a lot of talking done when we have that set-up.
EDIT: Totally forgot that minimum age thing... I'd say there shouldn't be one. Perhaps for online multiplayer, or at least the mics on that, but otherwise things shouldn't be restricted.