If you're speaking of what one might call "political" power, rank and status
within society, then Gandalf aka Olorin would probably be the last person to
consider himself of higher stature than Galadriel, since Tolkien repeatedly
described him as being humble, seeking neither praise nor reverence nor
power. In terms of "power" as what one might call "magical ability" all
of the Ainur, being angelic spirits and a kind of being completely different
from both Elves and Men, then Gandalf would probably have greater power than
Galadriel, since the Maiar who were sent as the Istari were supposedly "mighty,
peers of Sauron" who were forbidden to use that might to directly contend with
him. Interesting question,
though.
