Re: iron Man's first flight or Superman's (MOS) first Flight?
Iron Man. While both were CGI-fests the Iron Man one didn't feel like it. Plus it actually had story building elements in it rather than just "ok I learned to fly, well got that checked off the list". Iron Man's flight also had elements that would come into play later in the story in a very organic way(icing problem). MoS's ain't got anything like that.
There's no such thing as a movie that's too big to fail.