My first starter was Charmander. I got myself FireRed version and couldn't decide on Squirtle or Charmander. I knew enough about the game to know that your rival picked the one strongest against yours because my brother had LeafGreen and got all the way to the Elite Four. So, since I liked both, I chose Charmander because I knew I would still see Squirtle.
Pikachu, my first game was Yellow.
My best friend kept telling me about her's (i.e "I caught a zubat") and when she finally actually showed me, that was it. When my mom picked me up from her place I asked to get it and she agreed.
My first personal game was Platinum and I chose Piplup. I had played Sapphire before though but I didn't choose the starter I just took over my brothers save file which was abandoned at Lilycove and he had Blaziken and helped me get to Kyogre which I caught with my master ball and used strictly him the remainder of the game. Used only kyogre. Got him to lv 100. That was my first.