Not to be argumentative but Trent Richardson had one of the highest RB pre-draft ratings in history from nearly all major publications and that didnt turn out well at all. He was viewed as the best RB prospect since Peterson and a cant miss franchise changing back. McShay had/has them as the 2nd/3rd best RB prospect of all time - coincidentally enough Barkley is tied with Richardsons rating.
Also, while there are several 1st round backs that are great I can find just as many that are as good or better that were drafted in later rounds using much much less draft capital (Bell, Hunt, McCoy, Howard). I also grant that this isnt a truly fair comparison because theres way more 2-7 round picks than 1st round.