Are all gods and goddesses naked?

In order to be naked, they would first have to have bodies. When they did, they were invariably clothed, because there are stories in which they make a point of noting that the god or goddess was disrobed. You wouldn't need to make that distinction unless the figure was normally clothed.

Look at it this way - the Greeks gods were just an extension of the Greeks themselves. And contrary to common belief, the Greeks didn't run around naked.