When and how did Naruto choose to be reincarnation of the Sage? And could other hardworking shinobi's like Rock Lee become the sage aswell?????
That's just a stupid argument... Naruto is fit to be the sage's reincarnation because he share the same beliefs as the sage.
Naruto never chose to be the reincarnation of the sage :| right now he is only trying to protect the world, he himself doesn't even know what he is. He chose to be the child of prophecy only to prove that his dad wasn't a failure...
Naruto followed his own path and that's to never give up. He chose to fight to protect his friends... That's the reason he is the reincarnation of the sage. Because of his ideals and beliefs he stayed true to (which is the same beliefs the sage had), even when others tried to prove him wrong.
Rock Lee chose to stick to his ninja way also, even when others told him that he can't be a ninja. Now look at him. He chose his own destiny.