As a little kid and still I guess, I have always loved superheroes.  My favorite ones have always been marvel characters (minus the Green Lantern).

In my opinion the greatest Marvel characters are obviously the Avengers.  Who the true core team is always in flux as well as who is indeed their leader, their affiliation with S.H.I.E.L.D, which stands for Strategic Homeland Intervention, Enforcement and Logistics Division.

The core Avengers though are: Iron Man, Captain America, The Hulk, Thor, Ant/Giant Man, and The Wasp.

Personally I think it is all about Iron Man.  Tony Stark is a normal human, with no powers of his own except for what he can create. Allow though he is a genius, he lacks the physical supernatural powers of the others.

Although he is not as strong as the Hulk, courageous as Capt. America, or commands the power of Asgard as Thor does, he is still perhaps the most capable warrior of all.  His ability to adapt to any circumstance is what allows Iron Man to always come out on top.

Truly the Man in Steel or rather some other incredibly rare and unknown metal has the brains, power and ingenuity to be the greatest Avenger.