My first starter pokemon was either chikorita OR bulbasaur. It's a tie between those two, because I used to play my brother and sister's games while they weren't around and I can't really remember which game I played first. Those were their games though not really mine so it technically wasn't my own starter pokemon so if I had to say my first starter pokemon would be Piplup.
Chikorita from SoulSilver - still my favorite game, even after playing older and newer pokemon games! The pokedex was -in my opinion- at its best in SoulSilver and HeartGold.
Squirtle in Blue. I don't remember much of him, though, aside from spamming Skull Bash and Hydro Pump with him.
The first starter I formed any real attachment to, however, was Blazealote the Blaziken (yes, I know, stupid name) in Emerald. I loved her so much, but sadly, I don't have her anymore. Talking about her kind of makes me want to IV breed a competitive Blaziken in honour of her...
My sister had Red, and would let me start a new game but not save. On that, I would choose Charmander. For my birthday she gave me Silver and I picked Chikorita. I guess Chikorita was my "official" first starter.
Cyndaquil... I named him Quillo c,: Typhlosion will always be my favorite starter and Johto will always be my favorite region, I'm kind of nostalgic for them.