My first Pokemon was Charmander on my sister's Red Version. I originally wanted to pick Bulbasaur because I had heard that Bulbasaur was good for beginners, but my sister told me that Bulbasaur was her favourite and I couldn't pick it as long as I was playing her game. So I picked Charmander instead. This was way back in 1998.
I think some of the other Pokemon I trained back in the early game files were, for the most part, basic run-of-the-mill wild Pokemon - i.e. Rattata, Pidgey, Butterfree, Oddish...