Rummy has it. There is a more to iron man besides the Bullet proof suit and crazy firepower. He is a technical genius. He could easily plant a virus within the terminators armour, and he has the infinity gem, and of course, he can fly.
But if you had to put it down to just Iron man's suit and skill, I would still say that stark wins. His armour can withstand a tank shell, he can fly, he is agile, his punch, which some people underestimate, is actually VERY powerful, and he can throw out many punches before the terminator could swing his powerfist, and stark could probably dodge the powerfist. Also, starks uni beam, I believe, is about as powerful as a melta gun.
The terminator doesn't stand a chance.