My three year old has only known about MAME for about 3 months. He is happy playing Superman and can fly around and kick the bad guys. He sucks at frogger, unless the point is to be hit by the very first car every time.
What he likes most is when he dies the game restarts and he gets to watch Clarke Kent run accross the screen, turn into Superman and fly off.
This preceedes about an hour of my son strutting around the house saying "I'm Clarke Kent" then he puffs his chest out, takes off his top and flies around the living room

We had to buy him a laptop "mimi-mouse" when he turned 2 because the big one on my PC was too big for him to hold. He "got" the mouse at that age and has been navigating the PC playing flash games...... he recommends "Postman Pat".
About 6 months ago he actually taught his mum to copy a DVD in DVDshrink, open up a dvd printing app, design a dvd printout, instert the dvd-r into the printer caddy and into the printer, and print said design onto the dvd-r...... Bless his pirating little heart.

His mum had never done this before and just took his word for how it was done.

Probably a good job he can't spell or I would have to put NetNanny on the PC.