Wargle
Dirty minds think alike~
Brock
Well, experience requirements are based on the levels pokémon evolve at, rather than their relative power. The starters reach their final forms fairly early, so they don't have any particular experience requirements, and I'd prefer not to make a bunch of exceptions to the usual EXP progression to account for perceived power differences. In any case, how much EXP would you consider to be appropriate for them?
I would say 3/4 to get to middle stage, and 4/5 to get to final stage. It really depends on what you want to make them. I would say 4 to get to Venusaur, Meganium, Empoleon, and Sceptile, while 5 to get to every other starter, but this list might be somewhat Biased.