Hm. Probably visiting my neighbours' house when I was three and watching their kids playing Sonic the Hedgehog on the Sega Master System. After that, it was watching the Donkey Kong Country intro over and over again on about thirty TVs at a nearby Big W. Since the SNES was still pretty expensive but the Master System had gotten much cheaper and it came with a free game (the BIOS version of Alex Kidd), so my parents got one of them for the family and a couple of games. Alex Kidd in Miracle World, Castle of Illusions, Ghost House.... even today those three games instil instant nostalgia.