My reservation about Williams would be around the fact that USC wasn't better. *Generally*, an NFL all-pro caliber QB is such a huge advantage to an NCAA team they can't help but be pretty dominant if the team has any kind of overall talent level at all. Maybe USC was just that bad, but that would be my issue. Even Brady, who no-one thought was that good at the time, finished his senior season leading the #5 ranked team in the country.
Off the charts physical talent is no guarantee in the NFL where being able to think the game fast is more important than any physical skill.