Wait, I just remembered...in Yellow version Pikachu was a starter. XD That was my favorite start as of yet. It is true that Chikorita and Treecko might be harder to train, but Bulbasaur was fairly easy. Those who choose Charmander had to trainer more because the first gym leader had rock-types. *Same for Ruby/Sapphire version, it is a rock-type trainer*
For the Gold/Silver series, the first gym leader had flying types, so those who had Chikorita might have a harder time.
Anywho...Pikachu is the best start and I rest my case because of my personal prefrences. ^___________^;;