Dwight being in this discussion is a bit disrespectful. Dudes been to the finals, multiple all stars, multiple all nba and defensive teams, multiple DPOY's, multiple rebounding champ, multiple blocking champ.
Clearly the answer is CP0, he has played with better players than melo ever has and has yet to even make a conference finals. If paul wasn't always being labeled a top 5pg of all time, I would of said Melo is the biggest disappointment of the 3, but a top 5pg of all time should sniff a finals atleast once with 2 other top 25 players in the nba (according to espn).
Melo, his fault or not, has noy played with a superstar his entire tenure with the knicks, forget superstar but I think his entire tenure with the Knicks, he's only had 1 allstar player and tyson chandler only made it because the center position was weak
Edit- And honestly if it wasn't for jr smith getting suspended, that team should of gone to the ECF that year