I believe the most talented of the three you mention is Charles and I'm tempted to say he's in a class by himself compared to the other two you mention. The problems I see with Charles stem with immaturity as a ball carrier. Either as a kid or an adult, have you ever gone to the park or gym and watch someone "athletically show off?" What I mean by this phrase is the person in question deliberately makes difficult choices because he wants to show others he can be spectacular. I believe Charles sometimes did this as a runner when he had to make choices at the line of scrimmage. I saw this happen on a few plays against ASU. It just appeared that he tried to make more difficult cuts when there were easier runs available. On the one hand, it takes great vision to see what he saw at the line of scrimmage, but it's like he was too hooked on the idea of showing everyone else that he had great vision rather than gaining yards for his team. I'm not saying that's really his singular thought process. Who knows what he's really thinking, but I've seen athletes, musicians, or performers who always go for the high-risk/greatness play that few could even see or conceive fully regardless of the situation. Charles sometimes did this--it also fits in with the bravado/confidence he had as a freshman to say that he was going to make people forget about Adrian Peterson . I think Charles has the best natural instincts and total package, but he needs to protect the ball and not over-think what he's going to do. Some guys look like they are thinking too hard and play deliberately as if they are worried about making the right choice. Charles situation is different. I watched some plays where I thought "that was a weird choice," then I rewind and break it down and see that he saw something that could have resulted in a huge play. The problem is he was decisively playing as if you could hear him in a split-second saying, "find the most diffcult, bad-### play I can make and go for it." If he took what the defense gave him more often--ala Ray Rice, he'd be one of the best in this class. I think he has Marshall Faulk-like skills in many respects.
Jones? I really like the little I saw of Jones as a behind the line of scrimmage TB. But 1/2-2/3 of his carries seem to come as a WR on an end around in the 6 games I watched of his. I think he'll be a fine situational back with the opportunity to develop into something more if he demonstrates he's capable. The best word I would use for him as a running back is "unproven" at the college level. As a runner (kick return, open field, situational guy on end arounds) he's proven he's a heck of a football player. I just find it difficult to project him confidently as an every down runner when he's only had one 20+ carry game for his entire college career. Does that mean I won't take a chance on him at the end of the first round if he fell to me? No. I'd snatch him up in a heartbeat, but it doesn't mean I have him as high as many. Nor would I snatch him up as readily if I had a mid-first round pick in a rookie draft.
Johnson? Speed is amazing. Very fluid, too. I have him and McFadden fairly equal and both have the potential to become more than what I see from them. The difference is that I think Johnson is regarded by teams the way the Titans may have mistakenly regarded their RB pick last year. This is the right way to regard Johnson--an unfinished product who will provide situational explosiveness with the potential to become a huge threat as he continues to learn as long as expectations aren't for him to ever be more than a 12-15 carry/gm player. McFadden is discussed as if he's a 20-25 touch/game player who will run over people and grind it out and that's where I think people are mistaken. Johnson's balance is nice and he does some things that are very impressive, but he's a bit hot/cold when it comes to consistent, good techniques and choices. I like him, but wouldn't feel comfortable counting on him at this stage. The Westbrook comparisons I sometimes heard were off to me. Westbrook was a more polished player out of school, just from a small school and had to prove he was big enough to compete. Johnson seems to me like some circles are giving him the credit Westbrook had to earn and that's a mistake. Plus they are different style of player.
Mike, I'll have to send you a bribe if it were a call-in show...plus you can always find the number to the radio shows in Seattle and KC that I've been on on for years now...
I thought EBF was E.F. Hutton?
I'm sure you jam the phone lines when you're on too, right? I will accept the bribe though. What ya got? 
