Kal has his work cut out for him. I guess it depends on who is more likely to hurt the other. Godzilla was slow as molases, but he was also huge and very durable. Quite unlike anything Kal ever faced before. However Kal's super speed, flight and size make it almost impossible for Godzilla to actually hit him.
When it comes to Superman speed, size and flight matters the most but when it comes to Avengers , none of those matters , they get stomped BUT it doesn't matter they both get stomped superman has no way of putting Godzilla down either !
That's right, they don't but Iron man and Thor have flight and speed but those features don't even get mentioned in Avengers vs Godzilla thread but for Kal !! That's another story right! I agree that Avengers lose but it's the same for Superman he either lose here or it's a stalemate .
I don't know about the Avengers thread you're talking about, but I think it will have something to do with neither Thor or Iron Man having the necessary strength and durability(Iron Man) or speed(Thor) to pose a real threat to Godzilla. Barring Thor flying through the Ice Giant monster. I don't see that happening to Godzilla.
Either way I'm with you. Kal will most likely stalemate or lose.