You are shitting me tendoboy.
I don't know anything about developing 3D games...but didn't ILM lend SEGA their actual Iron Man models for the video game?
It is likely they had the models to use as a reference or for those models only they went through the conversion and retooling process. The only time you could directly use such models is if for some reason movie were using polygons which they wouldn't thats assuming the polygon count of the model in question was not ridiculously high or they took the model and rendered it to a 2d sprite. In Star Wars Rogue Squadron's behind the game feature where they show you how they went about developing the game had a section where they talk about splines or NURBS from ILM and the work they had to do to make them usable in a game.
There is a reason why movies uses splines and it is in the wiki article.
In computer graphics splines are popular curves because of the simplicity of their construction, their ease and accuracy of evaluation, and their capacity to approximate complex shapes through curve fitting and interactive curve design.
To create the same curve in polygons you would use an absurd number of them to have a high enough level of detail for a movie so flat surfaces don't show up on a curve. It's easier to work with since the real world is made of curves. It's basically digital clay. The current implementation of splines for mechanical objects are
NURBS.
The reason why splines isn't used in realtime applications like games is because they are computationally too expensive to use and requires massively more programming work to implement compared to using
polygon meshes in an environment that is limited by the amount of computer power and time to render. There are plenty of other reason why polygons are used over splines and anymore discussion about it beyond this level is above the level of knowledge I have on the subject.
Lets just say programmers and mathematicians the world over has already looked at this question and had decided one set of technology for this purpose and another set of tech for another for some very good reasons. If they could uses one "Universal" system, there wouldn't all these different model construction/rendering/animation types/methods out there.