I would guess that great writers not only write exceedingly well, but can slide into the creative frame more easily. Or, perhaps they are better at not spending time out of it in the first place.
For a number of years, I was living under the assumption that I was going to be an artist of some sort. Not everything was great at that time, but I miss the way that I was taking life in. Meaning was closer to the surface, and serendipity reared its head more often.