My favorite licensed RPG and the greatest superhero RPG I have ever seen, read or played. I wish to heck this game was still in circulation today, but I own the full line, as well as a lot of fan material. I have never seen an RPG capture the four colored feel on the same level as Marvel SAGA, whose mechanics sing in spite of some troubling writing and editing flaws.
If the last couple of years of Savage Worlds hadn't been so awesome, this would have also been my #1 favorite RPG...and even then, choosing from this or Savage Worlds would be difficult in a pinch (but I'm sure that I would ultimately go Savage).
Just an under appreciated, and awesome, RPG.