For those who are fans; what singular game, if any, sparked your love for Nintendo and what specifically about that game inspired such a connection with you?

Try to guess it.

Super Metroid. Best game ever.
The music, mistery and ambience. The solitude and freedom of exploration. I played nothing like that before.

Sorry for my bad english.

Super Mario Bros. I had played some Atari and Commodore 64, but I played SMB at a friends house and that was it. I was in love. Got my own NES with SMB and later Mega Man 2 and several others. Bought, borrowed and played a lot of NES games. Good times

I know this is a cop-out answer but it was not a game, it was a system, and im talking about the SNES. Long answer coming: Before the SNES I'd say I was very casual about gaming as a whole, even the NES and games like Super Mario Bros and Mega Man did little for me. But I got very invested in the SNES as a whole, and I started following everything Nintendo did because of it - and boy did this system had a huge library of awesome games. Loved that era.  

Now, I know the expected answer for this particular question is something in the lines of  "this particular Nintendo game made me love the Nintendo company's products", and If im forced to that kind of answer,  it'd have to be A Link to the Past - Which remains one of the best Zelda of all time as far as im concerned. But I do believe I already had love for Nintendo beforehand, due to the system itself. 

Sorry for my bad english. 

Both your English is excellent, and please don't feel the need to apologize, even if it wasn't, going to the trouble of speaking a second language is a courtesy that you do us, not vice versa. :)

I'm not sure if I fit in the definition of Nintendo fan

I'm definitely not a fan of the company, neither fan of their values

I'm fan of their games, but so I am fan of Square Enix, Sony and Activision games

But yes, overall Nintendo is the studio the makes the games I enjoy the most. It started with Pokemon, I owned a DS and later a 3DS only for the sake of playing Pokemon, which is ironic because I don't even like the Pokemon games anymore

On N64 (I never had one myself, but I've spend hundred of hours playing in a rented one when I was 7 to 10 years old) I discovered Pokemon Stadium 1 and 2, Starfox, Mario Tennis, Mario 64, Yoshi's Story, Pokemon Snap, and Ocarina of Time.

I will be frank and confirm that I barely remember how Ocarina of Time was until I've played 3DS version more than a decade later

Mario 64 was awesome, but my favorite platformer was Crash, and I never enjoyed Mario Kart as much as Crash Team Racing. My favorite Mario was actually Mario Tennis lol

I loved Yoshi's Story so much, still one of my favorite OSTs to date. But I don't know, Yoshi doesn't look quite a franchise to "sell" Nintendo for me

I always find star fox 3D confusing and ugly and in reality preferred the 2D games

So yup, Pokemon takes the crown here. Not only was addicted to Stadium, but played a lot Snap too. The fact it had an anime to give support only made my love grown, although I was never that big of a fan of Pokemon animated series (I was a digimon fan actually)

Ocarina of Time. It was just the perfect game. I spent weeks arguing with a classmate in art class that Turok 2 was better. He loaned me OoT. I didn't even like games unless they were Mortal Kombat or bloody shooters. OoT just blew my 12 year old mind.

Super Mario 64 helped a lot as well. It was a cut above everything on PS1 by a huge margin. PS1 games felt like they were living in the past with a lot of 2D games, or games that didn't use an analogue stick. SM64 and OoT just moved the industry forward so damned much. Nintendo continues that today with BotW, and Odyssey.

While I started with with Mario on the NES, it was the Legend of Zelda IP in general that stayed with me through thick and thin. Even when I was a diehard Playstation fanboy, the Legend of Zelda always had a certain way of pulling me in. I even marathoned every mainline game leading up to the Switch and BotW launch, despite barely playing Nintendo consoles from the GC through the WiiU.

As for what drew me in, many aspects really.  The lore that leaves potential for a ton of fun theories, the mix between adventure/action/puzzles, and the fantasy world of Hyrule itself.  I think I can safely say that it is hands down my favorite active IP to date.

I loved arcade games and when I saw Super Mario Bros. on a department store tv I was thrilled. I really tested a lot NES games from rental. When I saw Super Mario World on a department store tv I was blown away to a height I had yet to reach. I followed Super Mario 64 in magazines for years and finally played it in a toys r us. Everything I hoped it would be! Super Mario Sunshine was the last Mario title that I loved unconditionally — and it didn’t deserve the amount I gave it, in many ways. Nintendo doesn’t deliver the “WOW” that it did in the 80s and 90s.

I loved a lot of Nintendo games but it was Super Mario who hooked me every single time as a kid.

I think the thing about Super Mario that I liked was playing until I lost a life and then watching a friend play until he lost a life. You were rooting for him and glad when he dies, all at once. Beyond that I liked the simple super power and race to complete a level. Do you stop for coins/lives or do you hurry up? The design was fun as well. Colors and shapes were easily recognized and quite interesting. The feelings of each level were intensified in Super Mario World. I could feel the sounds and colors 😳 the games played with my feelings in a happy way.