Here's the reason Hulk can't beat Superman: mobility. Superman can easily remove him from the arena, and yes, you can remove people without throwing them into space. Remember, Impulse lost because he ran out of bounds and I'm pretty sure he wasn't running straight up.And I don't think Sue can beat either Thor or Superman. And I'm not going to vote on the basis of her hiding out the whole time.
And Superman has defeated Thor before. So I'd put it:
3. Invisible Woman
Hulk is not the strongest one there is, no matter how many times he says it. He's kind of an unreliable source.
Thor's lightning is directed by magic. It does not count as an actual magical attack.