You can have all the ambition in the World, but if you don't have the desire and Willpower to fight for/protect what it is you want, you'll never be great. Whitebeard wanted a family, and the strength to protect them. His resolve was so solid that he even went to War with the entirety of the WG in order to save a single crew member. The man, before his death, was the embodiment of Willpower. It's a shame his sickness nerfed the hell out of him. I'm really hoping when/if we get a God valley flashback, Oda really showcases what the Old Generation legends were made of.