My first contact with Nintendo was my sister's NES Clone with one of those 1 in 100 carts. I played Super Mario Bros., Balloon Fight, Donkey Kong and Ice Climber there (as well as other third party titles like Adventure Island, Galaxian, Yir Ar Kung Fu and many more.

My first introduction to Nintendo was the NES as one of my first jobs was working in a store which was selling the NES before any other shop in the town of Yeovil. It was mainly a TV repair and electronics retailer and the specialist nature of the shop meant there were periods without too many customers. I was basically paid to play super mario bros a lot of the time as that is all I was doing. It was only a small shop so I was the only staff member except at weekends.

My cousins family had a NES. She was off to school a week when I visited, while I was to young. When she came home we ate and then played Super Mario Bros 3 with game genie. Used codes to jump in mid air and gain infinite lives. I tried some games alone as well but could not use the game genie. Played Ice Climbers and Spy vs Spy as well as Super Mario Bros 3. Never got far and did not understand Spy v Spy at all.

I might have come in contact with the system before, but me waiting for my cousin to get home so that we could play Super Mario Bros 3 together with cheats is the earlies memory of Nintendo ad gaming as a whole I have,

I saw an NES in action for the first time over at my mom's friends' house back in like 1987 or early 1988. They had boys around my age, and they had an NES with several games. I recall them having Super Mario Bros., the Mario Bros. arcade game port, Ghosts & Goblins, and Section Z. Those games were all so far beyond anything I had played on the Intellivision, and I was immediately blown away by what I was seeing. I had to have one of my own, and in Christmas of '88 I finally did. It was the NES Action Set (the one with two controllers, the original grey Zapper, and the SMB/Duck Hunt combo cartridge), along with Jaws and the original Mega Man. Best Christmas ever.

EDIT: Actually, it would technically have been the Intellivision port of Donkey Kong, but it never registered to me that it was a Nintendo game. I was born in 1980 and Nintendo hadn't truly become a household name yet, so "Nintendo" didn't become a familiar name to me until I discovered the NES.

The original NES