[bilbo_baggins]

Gil-galad's descendants would not have had as close a personal cliam to the ring, Tuor because Isildur himself cut the Ring from Sauron's hand. You might argue that elves are wiser than humans, and therefore should control the all-powerful ring, but then again, they themselves are susceptible to the Ringlust (Galadriel's struggle), and are just as vulnerable as Men. In my opinion then, Isildur has the highest claim for the ring; his own descendant (Aragorn) has no more trouble than Galadriel in not taking the Ring.

I think that the Ring would not affect Smaug as much as you might think. After all, Smaug's confrontations with Bilbo proved that he could not easily be wiled and fooled. That and his inherent magical powers would combine to form his own personal magic mental block. That would also prevent Sauron from controlling him. Dragons were just too darn powerful.