Black Widow, Captain America, Hawkeye & Shield are a non-factor. Normal humans with military equipment haven't worked on Godzilla before and won't work on him now.
Iron Man is also a non-factor. He uses super advanced technology, but still even the most advanced inventions and weapons have never worked on Godzilla except for one famous example: the Oxygen Destroyer. Because Dr. Serizawa destroyed the blueprints and took the secrets of the weapon to the grave with him, Iron Man can't build one himself and has no other weapons to take Godzilla out.
Hulk is a tank and could easily match Godzilla's brute strength and even surpass it. The problem however lies in the source of Hulk's awesome power: radiation. Godzilla absorbs radiation and treats it like a food source. That means Godzilla could drain Hulk like a sponge taking him out of the battle.
Thor would be a tough opponent. Based on the comic crossover, Godzilla and Thor have equal physical strength so it comes down to their other abilities. Thor is faster and can shoot lightning, but Godzilla has hax regeneration and atomic power on his side. Lighting has a mixed history with Godzilla: in King Kong vs. Godzilla he was weak against man-made electricity, but in Godzilla vs. Mechagodzilla lightning gave him magnetic powers, and in every other film electricity/lightning does nothing.
It would be a tough, awesome battle (Disney, Legendary, Marvel & Toho need to make a crossover happen ASAP), but I give it to the king.
Why are so many people assuming that Thor Lightning is useless? if he wanted thor could focus all his energy into 1 blast (God Blast? not sure if his still has that power with no odin force) not to mention hurling the hammer at him using his full strength would have to do damage to godzilla, Thor is as strong as godzilla and mjolnir can absord energy and return it tenfold if i remember right, this is actually and even fight, Thor & Hulk (other Avengers help civilians) Vs Godzilla. Great Artwork!
I remember when I first heard that Godzilla used to be in Marvel comics and fought the Avengers, this is how the scenario played out in my head.
Godzilla appears in New york and starts destroying everything in his wake. The Avengers are called in to deal with him but find that the King of Monsters is more than just a lumbering giant reptile and while their heavy hitters seem to be able to damage him it doesn't seem enough to stop him and only seems to annoy him. Ant Man then comes to a solution, it is obvious that with Godzilla's size they won't be able to do virtually anything to him, let alone contain him so Ant Man gets to work on some devices that will use his Pym Particles to shrink Godzilla, mean while the Avengers try to keep him contained in a single area. Godzilla, now annoyed with the pests stops and tries to eradicate all of them so they will finally leave them alone which gives Ant Man just enough time to finish his machine and they shrink Godzilla down to at least the size of the Hulk. Assuming that the now shrunken Godzilla will be much easier to defeat and contain the Hulk leaps at him only to be tail whipped by Godzilla and sent flying, Godzilla then lets loose his famous roar letting the Avengers know that this wasn't over. While being shrunk did make him a bit easier to fight Godzilla was still as strong as if he was still giant and thus they were still hard pressed to defeat him. During the battle Godzilla fires his Atomic Breath at the Vision who turns intangible to dodge it however he was right in front of one of the devices that kept Godzilla small. Now destroyed there was nothing keeping Godzilla in his shrunken state and he returned to his gargantuan size and looked down at the Avengers like insects. At first they were just a bit of an annoyance but after shrinking him to their size Godzilla has had enough, they were going to pay.
I thought of the shrinking part when I watched Earth's Mightiest Heroes seeing Hank Pym shrink down Galactus (it didn't work because he can manipulate his size and just grew right back to the same size) as well as Godzilla keeping his strength even while shrunk because Ant Man said that the person who was shrunk kept their strength even when they shrink down. I don't know if that is how it is in the comics but it sounded cool to me. I also liked the idea that even if he is smaller Godzilla still wasn't going to be easy, I also thought it'd be funny for Hulk to jump at him thinking he was weak now only to be swatted by his tail. XD