The ring could have been destroyed a lot easier.

[obloquy]

Originally Posted by Raynor

I disagree; their only merit was the sending of the Istari. The wizards have failed, all to the last - that is, until Eru intervened, resurrected Gandalf, enlarged his power and wisdom and sent him back.

It was solely because of Gandalf's manipulation of events and people, and Saruman's research into ring-lore that anything was ever done about the Ring. In other words, the Istari saved the world. It's irrelevant that three of the five turned out largely useless.

Also, at no point did Gandalf fail. Eru's intervention was precisely because Gandalf succeeded not only in protecting his company and mission, but he had also conquered the moral test that Saruman had failed--namely, he maintained integrity to the Powers when confronted by an enemy that he really needed to open up against.

Lastly, there's no reason to believe that Gandalf's wisdom was enhanced. He was one of the wisest Ainur in his beginning, and was the wisest of the Istari from the start. Gandalf was enhanced with regard to the limiting nature of his incarnation and the rules he was subject to. Gandalf the White (and Olorin, who was presumably mightier still) was always a latent part of Gandalf of the Third Age, but was only allowed to be revealed after his true test of faith--that is, dying in abnegation of himself (to use Tolkien's word) to the Balrog. At that moment, though he had the power within himself to defeat that demon decisively, he remained loyal to the governing rules of his mission and kept his display of power in check.