the thing is once you get a genuine star you can build around that star.
you attract other players that might also be willing to take a paycut in order to play on a winning team with a chance of winning it all.
not only that but generaly have one of the best players in the game and one you know you can count on.
Once the hard part is done (getting said star) your team can get better as time goes on by trades/signings.
Superstar trades should never be looked at solely by the trade at the moment.
Did the Nuggets get a lot for Carmelo? Yes.
Does that mean the trade didn't pay off for the Knicks? Hell no.
The Knicks not only have the better team (say whatever you want about the team records (although Denver have been impressive to say the least), but the amount of injuries the Knicks have had to deal with would make a difference in any team), they have a genuine leader, a go-to guy (and a 2nd go-to guy in JR), and even though this team is old and won't be together for long they have the capability of building around him again (this time with younger pieces).
Just take a look at the Heat for example, it's true that they won the title last year, but they're even better this year.
The Heat have steadily been improving year after year since aquiring the other 2 amigos, when they made those signings the Heat had some great stars but a bad team, 2 seasons later and that team is capable of winning tough games without James & Wade.
A team like Denver, as good as it might be and as fun as they are to watch, won't win a championship, they don't have a leader, a go-to guy and when push comes to shove they don't have that "star" factor, I'm not hating on them since I really like that team but they're punching above their weight.
I'm just gonna put it this way, I don't see Denver winning the title, while I do give the Knicks a legitimate shot (and not as a 1 season title-or-bust team)