Marvel and DC both have Earth based shape shifters in the form of Sandman and Clayface. Each can be brought down with a well place gush of water, but if the two had to go against each other, who would win?
Sandman (William Baker a.k.a. Flint Marko) is a fictional supervillain appearing in American comic books published by Marvel Comics. A shapeshifter endowed through an accident with the ability to turn himself into sand, he began as a villain and later became an ally of Spider-Man.
First Appearance: The Amazing Spider-Man #4 (September 1963). Created by Stan Lee and Steve Ditko.
CLAYFACE (Matt Hagen)
The second Clayface, Matt Hagen, first appeared in Detective Comics #298. A treasure hunter, Hagen finds a mysterious radioactive pool of protoplasm in a cave. Immersing himself in it, he is transformed into a malleable clay-like form which could be shaped into almost anything he desires. This is only a temporary effect, however, requiring him to return to the pool periodically in order to maintain use of his powers.
With a bit of knowledge under your belt, it is time to throw them in the ring and have them fight!