I figured this is a decent match-up.
On one side you have Iron-man, which his most current suit of armor, which is the pinnacle of mechanical engineering technology.
versus
The Guyver, a kid(or solid snake if you go by movie 2) fused with an alien suit of armor that happens to be an advanced biological lifeform fused to the person.
They both have similar weapons at their disposal. Similar armor capabilities and such.
Iron-man has his Uni-beam, while the Guyver has his mega-smasher(boob-cannons).
Iron-man has his repulsor rays, while the Guyver has his gravity cannon and assorted lasers.
I think it's an even enough match-up.
Who comes out the victor?