The gameboy pokemon games.
If you didn't play them during that era, you will never, ever understand the pure awesomeness that are the first generation of pokemon games.
Everybody had those games, even many girls, collecting and leveling up your pokemon was just so darn magical at that time. You always wanted to see what attacks they would learn, and what they would evolve into. You watches in awe as your pathetic magicarp evolved into the badass gyarados. People battled each other, and traded pokemon with each other because you could get pokemon in red that you couldn't get in blue. The pokemon games really had the best multiplayer ever, for any genre, they made playing the games with each other a natural social thing on a bigger magnitude than any other game.
So many memories from that time. The time when pokemon was popular also happened to be during the happiest days of my life, in early elementary school.
So I heard Mario Madness during the NES days was the shit, but I still think I'm luckier to have lived through the trading and batteling and collecting of the pokemon madness era.