I don't any team except for Jordan's Bulls that has won an NBA title without a great center or great big man. So my vote goes for big man but today you need to have a deep bench, great coach and chemistry.
Greatness transcend positions. if you're a great player, it doesnt matter what position you play. If Shaq,Lebron,Yao,duncan,Kobe were all in the same draft, shaq would go first and you 5th. It doesnt matter the position, its the player. Yao is a good player, never great, but you can win with good, you dont build around good though.