the armor fit him. think about it: the Iron Man suit was basically built around Tony; it fits him perfectly and moves with him like a second skin. the fact that Rhodes was able to fit inside the War Machine armor at all, let alone pilot it, indicates it's not just the original steel car-smasher with more dakka, but a new suit that was built specifically for Rhodes.
shareIt's a pretty simple explanation if you watch the movies, and combine with some supplementary material:
1) The novelization of IM1 states Tony went to see Rhodey in the hangar because he wanted Rhodey to pilot the Iron Man armor. Rhodey declined before hearing the details, leading to Tony piloting the armor himself.
2) Nick Fury and Black Widow make a point out of the fact that it's not possible to "take" the armor because of Tony's security protocols. Look at what Rhodey did: he went to the basement, punched some numbers on a keypad, and (off-screen) instructed JARVIS to put the suit on him. Rhodey was authorized to use the armor. Absolutely zero room for interpretation here. If he wasn't authorized he could not have done that.
3) In IM2, Tony was DYING and giving away all his stuff. He made Pepper (one of two people he trusted) CEO of his company and starting giving his art collection to charity. He knew the world still needed Iron Man. Hence, he was going to pass that along to Rhodey, the other of two people he trusted.
4) Even if the Iron Man suits were not adjustable (and it is implied they are by how Tony can wear anything from a black bodysuit to a three-piece suit underneath it), Robert Downey Jr and Don Cheadle (and thus their characters, since there are no camera tricks to imply otherwise) are roughly the same height, weight, and build. What would fit one would almost certainly fit the other. And the characters are best friends and would know that.
Never hate your enemies. It affects your judgment. -Michael Corleone
He did try to recruit him in the previous movie. It was obvious to me that was what he was trying to do.
shareAlso, Tony's reaction when Rhodey came upstairs was "Why don't you put that thing back where you got it?" not "How did you get that?"
Never hate your enemies. It affects your judgment. -Michael Corleone