The Nintendo DS was my first console, period. When I was really young, I was given a DS Lite. I think I was 4 years old at that point, but I can't remember for certain. A core memory I had with it was getting Super Mario 64 DS for Christmas, playing it, jumping around Peach's castle as Yoshi, then thinking to myself, "Oh, that's the whole game! This is fun!"
It wasn't until a year or two later when I realized I could go into the door to Bob-Omb battlefield.
I did so much on the DS as a kid, it was my favorite. And all of my friends had one too, so we would play games together, like New Super Mario Bros DS VS, Mario Kart DS, pretty much anything with download play.
This was also the console where I had my first experience with Pokemon, as I played Pokemon HeartGold in 2010. I remember naming myself "ASH" because I thought I had to, and choosing my favorite starter Pokemon, Cyndaquil. Later, I would get Pokemon Black, and getting lost in Unova. I also got the event Victini, and he would quickly become one of my favorite mythical Pokemon.
This was also the console where I would play through my first Final Fantasy game, Final Fantasy IV. I got it after my dad had finished it, and I would get really far through it as a kid. I got lost in that world, and the voice acting in the cutscenes was beautiful. The art style really stood out to me, because I would not see any other games with the unique polygon artstyle that it uses. I wouldn't beat the game until I was in high school.
Unfortunately, this story has a sad ending, because I was gifted an action replay cartridge, and I would use it on my Pokemon HeartGold cartridge, trying to get Celebi because I had missed out on the event. In doing this, I lost my original save file, and the BIOS for my DSi had become corrupted, crashing on startup, not charging, and eventually bricking. I lost everything, years worth of flipnotes, stuck inside it forever. This taught me to never cheat ever again.