But is the myth true? Is honey really the only food which lasts forever?
This is actually two questions in one:
1) Does honey stay edible forever?
2) Are there other foods which stay edible forever?
The answer to the first question seems to be an unequivocal "yes." Thanks to a combination of hygroscopy, pH, and naturally occurring hydrogen peroxide, honey really never spoils.
As for the second question, it depends a little more on how you define "food" and "edible." A pile of salt never spoils, but it does not, in-and-of-itself, constitute food. Dry rice and beans will also keep for centuries, but they require substantial preparation to make them edible again.
What's more, honey is both eternal and edible with very little human preparation involved. Basically, the recipe could read: "Extract honey and put it in a jar."
With just a little more effort, there are a small handful of other substances which could plausibly hold the title of immortal food, molasses being one.
But why quibble? Honey is amazing and you can learn so much more about the magic of its eternal existence at Smithsonian.com; they have an excellent summary of what makes honey immortal.
 "Thank you, Dan, for really moving the ball down the court on this conversation..."
 At least for relatively small values of "forever."
 Despite Ricky's claims.