Cue: a bunch of generalised statements.
Proportions: everyone's too thin. In reality, men have shoulder width of about two heads, a bit less for women. Hips should be roughly the same, two heads, a bit wider for women, a bit less for men. Now, you've got kind of a chibi thing going, so the proportions are supposed to be off, but it seems like you've nearly drawn regular-shaped people with doublesize heads, which is definitely wrong, chibi or no. I really think you'll get better results if you draw bigger torsos and wider hips. Your eyes are generally too close together - ideally, they ought to be a eye width apart.
Colours: You gave everyone the same skintone, even morpheus and that black parade skeleton, which is really weird. You shouldn't even use the same skintone for every white character, in my opinion - you should pick them to suit the rest of the sprite, or to contrast with other parts of the image or game they'll go in. In a lot of places you're using too many colours to represent one thing, and it loses a lot of readability, almost like the lossy compression on a jpeg image - I'm talking about the costume on that first wolverine, the face on Barbossa and Goku's hair, as examples, but it's there throughout all your stuff. In a lot of places it just lacks contrast - the whatever-it-is in front of the waterfall is entirely unreadable, and the "READY FREDDIE?" one isn't much better. I don't know how you managed it, but the black and white on the Black Parade dude's costume lacks contrast, too. Basically, I think you're not picking colors that compliment one another. You should really read a bit on colour theory if you haven't, and keep it in mind.