Ho gawd, I have no idea.
I do know that my brother had a PS2 when I was really little, and seeing as I was already dominating Heihachi with Christie in Tekken 4 when I was 5 (my brother was 15 and he couldn't even do it, lol. That must not have been fun when the 5 year old beats a boss that you nor any of your friends that you had over at the time could beat. xD) it was most likely . . . something for the PS2 when I was too young to remember.
I also remember that I had a PSOne, my dad had a super nintendo . . . er, SNES(?) that I used to play the original Mario games on, a lot.
Whatever it was, I know it was not Pokemon. I don't think I actually picked up a Pokemon game until . . . sometime after getting my first GBA SP for Christmas when I was 5 or 6, and even then I think it was either Blue, Silver, Yellow, or Crystal that I played first. Most likely Blue.