There's a lot of artistic license in the way the movies present Tony Stark in the Iron Man armor. It makes sense, after all, that you'd want to see your star's face, speaking and emoting, and the "HUD view" is a damn sight better than the way so many heroes unmask so incessantly on film and TV (the Spider-Man franchise is a major culprit). And we accept it even though there's no way a camera would be that far away from his face inside the helmet. It's a representation, not the reality.
But what if the helmet was actually designed that way? What might it look like? Well, Jack Kirby already put some thought into it. Check out Captain Victory's "HUD" from his very first issue: