Before I really knew what anime was one of my elementary school friends introduced me to Cardfight!! Vanguard. My first anime that I knew was anime was either Ouran High School Host Club or Fairy Tail.
i think my very first was pokemon, i watched it on the tv when i was a kid. i remember the second one was ghost in the shell and it was too strange and scary for a lil me lol
Mine is between Cardcaptor Sakura, Inazuma Eleven and Dinosaur King. Though I remember vividly as a child, waking up early with the sole purpose of watching Dinosaur King on TV without even properly knowing what anime was, so I reckon it was Dinosaur King.
Likely Shaman King (I say likely because there are other animes I also watched during that same period of my life... Any one of them could be my first anime lol)