Pokemon probably wouldn't have made it past gen 1, at least in the US. There, blue outsold red, and I don't think that'd be the case if primarina was on the cover instead of blastoise. Primarina also being so girly looking may have even been enough to prevent boys from wanting to buy red. Chesnaught is ugly and brutally unpopular but so is venusaur so I don't think that switch changes anything. The real question you're asking is "would charizard alone have been enough to carry this franchise out of its infancy," and I wouldn't rule it out but I don't think it's likely.
