He staved off a natural disaster by messing with the alignment of tectonic plates in "Planet Hulk"...
Moving a planet is beyond his ability, I would think.. A feat of his strength causing California to become an island is more "in his ballpark".
Comparing DC heroes to Marvel heroes never makes sense to me.. the two universes are sewn from different cloth.
Now I'm interested in tracking down Hulk #300.. thanks!