I think that sometimes - and if you've ever written anything of your own you will be familiar with this - you have this great idea for a character but when you try to actually write them it just doesn't work the way you want. You forget that the audience doesn't have access to your notes, they only see what's on the finished page.
So sometimes you will 'create' a character who's supposed to funny but you, the writer, are not actually very funny so the character isn't either. The other characters stand around and say things like, 'Oh that guy is just hilarious!' but he just isn't. This happens a lot. You want the audience to take a villain seriously but the villain just gets his ass handed to him constantly. You want two characters to fall in love with each other but the relationship is an Anakin/Padme-level unconvincing disaster etc.
Iron Man in the comics is basically that and has been since his inception. We all know that he's supposed to be this smug, womanising drunk; a kind of flying, smartass Don Draper in power armour but he's usually just written as a bland, exposition-delivery robot who occasionally dabbles in fascism.
The movies did a far better of job of conveying what Iron Man was supposed to be (look at Stan Lee's comments about the character, for example. Iron Man was basically created for the sole purpose of fucking with liberals). They're vastly more interesting.
The other thing about Iron Man is the character was really before his time in a lot of ways. This is a twenty-first century hero. The tech, the hypocritical philanthropy, the terrorism, the celebrity culture, the futurism etc. It's just Super Steve Jobs. This is Iron Man's moment. This is the kind of hero people want right now. He's never been more relevant.