Bill played seasons of (in order) 35 games his rookie year, then 51, 65, 58, 14, 33, 55, 67, 80, and 10 games.
He never managed to play a full season nor average as much as 35 minutes per game in any one season.
Walton is done, while Greg has a much higher ceiling still possible.
He is young enough that he could end up with all kinds of rings and things, eclipsing Walton's accomplishments.