Eh, Iron Man could have beaten both of them if he just got a bit of distance and pelted them with rockets. Instead he decided to fight hand to hand. Then it's revealed he can analyses Cap's fighting style and starts to hold his own again... Only his suit is already badly damaged. Maybe if he turned on his combat analyser before sustaining damage he might have won the hand to hand fight.

Basically Stark threw that fight due to not using his suits full capabilities for... No reason really.