What do think is missing?
It's not so much what's missing, as how he is portrayed. In the 80s and 90s when I was collecting and reading IM, he was more serious, less silly. He was smart but not witty -- the movie IM seems more like the comics Spider-Man in that regard. He would never wear band tshirts, would never poke fun at teammates, etc. In the comics he could be a good team player, and was less narcissistic, too. I liked the comics Tony Stark as a personality and hero, but I find myself actually disliking the movies Tony Stark as a personality, and he doesn't seem like a selfless hero.
For instance, the entire plot of
Age of Ultron -- all the deaths, all the destruction, all the near-total-annihilation of all life on Earth -- was due to Tony Stark being an ass and making a super-powered murderbot behind everyone's back. And after all that, he walks away from it apparently without any guilt in his mind. (And I really, really, really liked the
Age of Ultron movie -- I saw it 3 times.)
But then, the Thor of the movies is quite different than the Thor of the comics (of my time), too. But I don't find myself disliking Thor in the movies -- as a personality and hero.
Bullgrit
I'm about to go on a 3 day vacation, so I probably won't be posting for the next few days. FWIW.