I was noticing the uniforms worm by the soldiers in attendence at President Obama's speech at West Point. Currently, the Army's equivalent of a suit is the Class A, or Dress Green uniform. It's the one you usually see them wearing when they testify before congress, for example. See below. (Click any image to enlarge.
At West Point for the speech they were all (except the cadets, who have their own uniform and wierd rank) wearing their Dress Blues, stepping it up a notch.
BTW, there is an even dressier uniform, called the Dress Mess uniform.