So it's power sets that make things equal? Luke Cage and Hulk have the same strength then, because they both have super strength? I won't insult you by listing the literally thousands of other examples that prove this train of thought wrong.
M'Gann's set hasn't been shown to be on the same level as J'onn. Same powers or not, it doesn't mean each of those powers is equally as potent. Particularly when the opposite has been proven true more than once.
You may have a point with Amazing Man/Absorbing Man. But a lot of that logic is flawed. And lulz at listing all the things you don't need him for anyway. Nice touch, that.