This just goes to prove that with any trade, it's not all about X's and O's, or sheer talent over role players.
You have to consider everything: salary compensation, team positional needs, and just as importantly, TEAM FIT.
Unless you're a top 5 talent a la Lebron & D-Wade, it is absolutely detrimental to the development and chemistry of your basketball team by bringing in multiple one-dimensional players. For example: players that need constant ball touches to thrive, offensive-minded only players, players that play in the same area of the court, etc.
Melo and Amare, while unquestionably offensively talented, were never known to have improved their surrounding teammates nor were known for their defense. Add those two together w/ a Mike Antoni... and well... here are your 2011-12 New York Knicks.