Despite his flaws on covering the running game I do think his pass covering skills more than made up for it, especially considering that's the greater part of a cornerback's job. I don't think there has been a person at the position that has surpassed him since he played, but ratting him as the best ever isn't as easy even if he very well might be the best.
Part of the problem is that there were many good corners that played before him that didn't have his flaws and were pretty good in coverage also. Also, the fact that they played in a different era makes it hard to completely and fairly compare them though. It's not quite apples to oranges as a comparison, but there is a difference enough between eras it's not easy.