The original Gameboy, I don't remember the first games I played but I remember the intro music for one of them and some of the gameplay of another one, and that song was stuck on my brain for almost 2 decades and this bugs me.
3DS and apart from the game that I got with it (which I promptly sold afterwards because I ended up not liking it), I think it was Spirit Tracks and a New Super Mario Bros (because OoT3D came out a couple of months later)
Mine was a black Gameboy Advance when I was about 6 (I think i got it when it was fairly new looking back at its release date).
If I recall, my first game was Dokepon, if it wasn't then it was the first game I played properly on the console itself. I actually still have the console and the game and all of which are still in full working condition despite the age and wars they've both collectively been through. Sometimes I just like turn it on and get that nostalgic feeling, reminds me of playing it on the coach when I was on holiday in Italy.
a game boy advance and pokemon yellow
last time i saw the gba was like late 2nd grade and till this day neither me nor my brother know what happened to it [though i gave away pokemon yellow to my friend due to me not liking it]