I'd agree with that if you took Charmander, but otherwise Brock is pretty easy. Still, I usually get myself a Butterfree to learn Confusion and then you can actually do some damage to his Pokemon.
Hardest first boss? I really don't know, actually. I suppose I could be a pain in the neck and say the first boss of Shadow Hearts (SPOILER)Albert Simon because you can't win that fight![]()