My first Mario memory was in the late 80s, seeing a friend's family get a Nintendo, with the SMB/Duck Hunt cart. We all were still very young at the time, and had no idea that the game was longer than the first four levels. It was hard enough for us as it was, and we literally thought the first Bowser's Castle was the end of the game. So imagine our surprise, when an older kid came over, and beat World 1, revealing World 2 before our very eyes.
Child minds = blown.
I eventually got my own NES, though "late", around fall 1990, and of course Mario 1 was my first real gaming crush (I had flirted with Pac-Man and Dig Dug and other games in the arcades, as well as a few Atari and PC games, but I wasn't really INTO gaming into NES). But it was that Christmas, when I got a package that included, among other things, a copy of SMB3, that I had my first game that I absolutely fell in love with. Like madly in love, as in totally obsessed.
At some point I rented SMB2, and I'll fully admit that my initial experience with it, as a kid, was basically "WHAT, this isn't Mario!", because obviously it didn't play like the other two. But eventually I got my own copy of it, and grew to love it for what it was. I'll always love all four of the original Mario games (SMB4 = Mario World, obviously), but Mario 3 immediately became, and has to this day remained, not only my favorite Mario game of all time, but also my fav. video game of all time, period.