My first Mario experience, was actually my first gaming experience ever and gave birth to gaming for me.
I've been in the hospital for surgeries more than you can fill a phonebook worth. Back in 1993-1995 (not sure which year), I remember first playing Super Mario All-Stars in the hospital via those classic TV on a wheeled stand in bed. So at the earliest I was about 4 years old.
My first console was the SNES in Spring 1997 when I was finally able to get one. Yeah this was already after the N64 came out. :P But my first games were a doozy; DKC and Yoshi's Island. The latter cemented my love for Mario, and of course DKC is itself an extension of Mario.
In yet another stay at a hospital, and this would've been during a VERY key point in my medical history, I first got to play Super Mario 64 and Diddy Kong Racing in the hospital and these memories are some of the most precious of my gaming life. This was in an area squarely for children to play and have fun with games and have cool activities (I even baked cookies once!). This hospital was VERY gaming-friendly and was actually where I was introduced to Starlight Canada's handiwork, as they're to this day partnered with Nintendo to provide special kiosks for kids to play various consoles throughout the years, these were the two main ones I got to play during this era:
Yep, fully equipped with a VCR and a DVD player respectively!
So I grew out of this hospital before they got their Wii kiosk, but they made them and eventually Wii U and I think very recently Switch kiosks as well.
Outside of hospitals, Super Mario Sunshine was such a perfect "right place at the right time" scenario. Summer 2002 was a glorious period and this game was just golden. It's to date my fav Mario game of all time. Following that I bought Super Mario 64 DS right alongside the system at launch and I also adored and 100% the game fairly quick.
Mario, and Nintendo as a whole, have been part of my life since I was a wee toddler and are still a very important part of me to this day. Through thick and thin, especially when I've been seriously sick in the hospital. Pokemon was also a big part, especially when I brought my GBC and Pokemon Yellow one stay in 2001. Oh man I still treasure that occasion, pure magic. :)
Edit: Yep! Here's their Switch kiosk: