Essentially, everything IM can do/has, the FF can do/has (intelligence, strength, shields, flight, energy projection), with the advantage of being 4 targets IM would have to take out, to the FF only having one target to put outta commission.
Plus, even w/o prep, Reed may be better at coming up with on-the-spot gimmicks and tech solutions to problems. Case in point (and I hope I'm remembering this correctly): when everyone was trapped under the mountain (y'know, the one the Hulk was holding up), wasn't it Reed who figured out how to jury-rig what was available--using Tony's armor, no less--to blast their way out?
I think this would be a very cool, kickass fight. If Tony has his most powerful armor (Thorbuster?), I see FF barely winning.
__________________
Shinier than a speeding bullet.
With Iron Man's new Extremis upgrade, I'm pretty sure he can control multiple suits at a time, so I do think he has a decent chance of beating the Fantastic Four.
Realistically, IM only has to hit Torch and IW once each to take them out... probably the same with Mr F, the Thing is obviously much more durable but white noise would take him down just as easily as any other humanoid (in fact that could take out the entire FF at once)
Also Torch can't go nova without killing his teammates and at lower temperatures his flame will only give IM a large energy boost
Torch went Nova on the Hulk standing right next to the Thing and IW's force field has protected them from it more than once. The Thing beat Ironman when he lost control of his armor and it attacked Grimm in and Reed on autopilot just a few years ago. IM would only have a chance against the Torch using one of his more unconventional non energy attacks...Torch can be pretty versatile himself when he has to so I think those two are a good fight.
Ultimately IW could just crush him like a coke can on her first move, so this wouldnt really be a fight.
Iron Man is currently a lot more powerful than he was a few years ago since he got the Extremis upgrade, so I think it would be more of a fight than you believe.
Why wouldn't he, it says he has 2 days prep. I'm sure he will bring everything he needs to the fight including in depth files on each member. Ironman takes it with prep.
Ironman with no prep and a suprise attack with only his regular armor, then it will probably go to FF4, but Tony will still give them a run for their money.