It's a tough one but I think Imagine just slightly edges The Miracle out because Imagine doesn't seem to be as "naive" in the ways that it portrays itself.
That is like comparing Bohemian Rhapsody to Oops I Did It Again.
Imagine is in the Top Five best songs EVER.
Most definatly Imagine.
You can still be loyal to Queen or whatever, but you have to admit that Imagine is one of the best songs ever written. And The Miracle is not.