A while ago, I had a running debate with the ever-charming Brendon Connelly over at his blog about how to make Galactus work in the confines of the FANTASTIC FOUR movie franchise. He thought a straight adaptation of Kirby's character design would look awful, I thought SF/fantasy movies have a great tradition of giganticism (King Kong, Godzilla, LOTR's trolls, Balrogs, etc) and could look amazing if done properly. I've just read what the artist Eric Canete has to say on the matter at his blog, and I'll consider it the final word.
"I heard that in FF: ROTSS, Galactus is a cloud. And that the argument for this is because the people in charge of making the movie thought having a giant planet eater guy with a tuning fork-shaped helmet would look ridiculous. I guess... maybe. But the chrome man flying around on a surfboard, or the big man made of orange rocks is...not as ridiculous? It's entertaining how subjective taste can be, yeah?"