Re: *Spoilers* Problems caused by the MCU
I didn't like Iron Man because it was grounded. I liked Iron Man because the characters behaved like real people. It doesn't matter how fantastic the threat is. As long as your characters have a realistic response to the fantastic elements, its fine. This goes for Nolan's Dark Knight trilogy, too. It isn't realistic at all; the characters simply respond like real people would to the events of the trilogy.
"I defeated your uncle Victarion and his Iron Fleet off Fair Isle, the first time your father crowned himself. I held Storm's End against the power of the Reach for a year, and took Dragonstone from the Targaryens. I smashed Mance Rayder at the Wall, though he had twenty times my numbers. Tell me, turncloak, what battles has the Bastard of Bolton ever won that I should fear him?" - Stannis Baratheon