Sex sells, and they were both pretty sexual dudes, both in content and packaging, right? But while Prince's lyrics were far, far filthier (compare Superfreak to Erotic City), he had a leg up on Rick as far as accessibility goes, and there was nothing to be done about it. Why, you ask?
Because Rick James was a big, man-ass dude:

who looks like he may actually do something real crazy to you, whereas Prince is an elf:
And if I've learned anything since Peter Jackson's Lord Of the Rings trilogy came out, it's that bitches love elves.

Also, this.