ICONS is a fast and easy superhero RPG. The creation of characters is straight-forward and the challenge of coming up with a background for the sometimes oddly paired powers is fun. In most cases, you could have characters roll up a character and be playing within half an hour. One of the things that I most like is that these characters are "take me as I am." You don't level them, they are already super heroes for goodness sake.
Because of the simplicity, I find that running an ICONS campaign by email is very doable and maintains a lot of the fun.