Radagast, the absent wizard...

[Mattius]

It's always interested me actually that the istari must have had a mission and WHY was gandalf the only one to succeed ? What was it about gandalf's character of person that led him to succeed over others ?

Good question! I think in the Silm. or Unfinished Tales (can't remember which one) when Manwe is briefing the wizards before they set off Gandalf begs Manwe to stay becuase he fears Sauron. Manwe says that is the more reason why he should go. Thats why I believe Gandalf succeeded above Sauraman (who was too big headed but probably had the power to help counter Sauron) and Radagast and the Blue Wizards who were too weak.