G. Goku definitely wins because his training routine is far more intense than Saitama's. Saitama does 100 push ups, 100 sit ups, 100 squares and 10 km running every day, great, but Goku started his training in Dragon Ball Z with doing a minimum of that if not more at 100X Earth's gravity. thus is just the Saiyan saga, before he goes super saiyan. We later see Vegeta wanting to surpass Goku and training nonstop and pushing himself to the limit in 400X Earth's gravity but Goku is still stronger. Long story short, Goku works much harder and can easily beat Saitama. He had the original one punch in Broly's first movie too.