The Mirrorball Man wrote:
The Valar's "Wizard Initiative" was almost a complete failure, wasn't it? The blue wizards went native and disappeared completely, Saruman became arrogant, corrupted and ultimately, evil, Radagast spent more time talking to birds than fighting Sauron. And they had to reboot Gandalf before he worked properly.
It's thought that Radagast's mission was actually successful, though that assumes that his mission was to protect the flora and fauna of the world should Sauron succeed. The same holds true for blue wizards. One thought is the reason Sauron was stepping up his plans in the west was because at least one of the blue wizards managed to take control of the dragons to the east, and Sauron needed to find a way to counter that. Hence the heavy influence of dragons in Eastern culture.
Likewise, Gandalf didn't really fail. In fact, he sacrificed himself in order to help the mission at hand. He was "rebooted" partly as a reward for that sacrifice.