hmm, I'd say IronMan stomps.
FF were pretty crap in the movies. Reed was just a tinkering nerd with some interesting ideas, not the force that Doom is...
up against an IronMan who really was utilising his genius 24/7, with the kind of tech he had (Ai assistance, immense power generators, speed and velocity better than a jetfighter...) I think he'd more than handily beat the lot of them.
scenario, he surveils them with satellites, he launches missiles at them, uses the technique Doom used against Reed... just blasts Thing to pieces, takes Torch into the upper atmosphere and then into space if need be...
or easier/quicker still, he charms Sue Storm into bed with him. destroys the FF from within!
oh 'eck. second scenario IM loses.
Iron Monger doesn't add anything useful, in comparison to Doom and his resources.