Well we're reaching another milestone here with the 175th Masterworks (if you have all 175, take a bow!), so I think we're looking at a new number 1.  Marvel Team-Up was the 150th, so maybe we could have Marvel Two-in-One, but I'm going to play it safe and say it's Ka-Zar.... or Doctor Doom..... or Ghost Rider..... or Luke Cage.....