I remember reading an X-Men comic somewhere along the way where even his legs are impossibly muscular and well defined, but the above image was the closest I could find in a web search.
Anyway, my point remains the same. Men are sexualized right along with women in how they're portrayed in comics and movies, it's just that men are sexualized in different ways from women. And what's wrong with being sexy anyway? Last time I checked none of us were Puritans.
What we're actually arguing over is something different, we're really arguing over objectification. The question is, "Is Scarlett Johannson being objectified as a sexual object and not being considered a person in her depiction in the movie or in that poster?" Is she treated or depicted in a manner in which she is nothing more than an inanimate object, without personality, dignity, self agency, or respect, and solely for men's sexual gratification? And the answer is obviously no. She's a character with a personality that passes the Plinkett Test and everything.
That's not to say there aren't plenty of examples of women characters being objectified all over media, including comics. But objectification and sexualizaton are different things and we needn't clutch our pearls over ScarJo showing some curve in the same frame as three guys with biceps the size of your thigh. And let's be honest, knee jerking about sexism in a movie written and directed by Joss Whedon is a little bit ridiculous.