It’s a time-honoured trope of superhero comics: sooner or later, one or another of the various A-list supervillains will decide to gather all the other (and hence, lesser) villain under their command, and be-devil the heroes with them. There’s a number of reasons why this idea is flawed to the point of suckage, and why it should be given a nice long rest:
It’s been done to death
This is the first and best reason. We’ve simply seen this too many times. DC used it in Final Crisis, Infinite Crisis, Underworld Unleashed, and Crisis on Infinite Earths – as well as in several less world-shattering stories, such as the opening arc of Superman/Batman. Not to be outdone, Marvel used it in Siege, Dark Reign, Secret Invasion and Civil War, as well as, you guessed it, other, smaller stories. Give it a rest, guys.
It rarely makes sense
Most of the time, villains are recruited for it simply on the basis that they’re villains. Even if they don’t think of themselves that way, that’s the side they line up on, yet again, whenever someone needs the numbers to fill out a crowd scene. In fact, some writers at both DC and Marvel have implicitly acknowledged this by having their supervillains mind-controlled, which makes a little more sense.
It does a dis-service to the villain’s characterisation
It’s a rare case where such a gathering serves any villain’s characterisation well. Regardless of what their personalities or goals are, unless they’re one of the handful (at most) who are in charge, chances are they’ll be treated as interchangeable parts. Theives will suddenly become murderers, for example. And in doing so, they get blurred even more into simplistic villainous characterisations, making it that much harder to use them well afterwards.
It assumes a fellow feeling amongst villains that just doesn’t exist
The willingness of villains to put aside any personal grudges they may have against each other for someone else’s goals, usually on the vague understanding that there will be profit involved. Increasingly, villains become like lovers going back to abusive partners, telling themselves that this time it will be different…
This is not to say that it can’t be done well – it most certainly can. The Hood’s group, for example, made logical sense and still had indvidual characterisations; the Salvation Run storyline also featured reasonable characterisations and a logical reason for the villains to work together, along with the clear implication that it would all fall apart the instant that reason no longer applied. And smaller groups, such as the Secret Six or the Thunderbolts, can reasonably work, both logically and artistically. But a few counter-examples do not disprove the larger point I’m making here.
Which is this: Marvel, DC, Image? You need to find a new idea.