The Witch King versus . . . Elrond?

[Knight of Gondor]

Question: Is Tom Bombadil greater than Gandalf?

I note that Gandalf seems to know much of him, speaks of him almost as a brother. When he leaves the hobbits, it is to go have a conversation with him, and, almost as a journey's-end lament, says that Tom was a moss-gatherer, whilst Gandalf was a stone doomed to roll. This indicates that Gandalf had much prior knowledge of Bombadil.

I base my question also on the concept of danger. Gandalf says that he is "more dangerous than anything you will ever meet, unless you are brought alive before the seat of the Dark Lord." Depending on how much power one reads into the concept of how great a threat one can pose to one's enemies, this indicates that Gandalf is greater in might, even than Iarwain.