in my opinion the statistic which gives the most weight to a players abilities are the qualitative statistics which measure average performance per effort. for example, average yards per carry. earned run average (era). pass completion %. batting average. 3 point %. sacks per season. etc.
that being said, other considerations should also weigh in. for example, performance under pressure. quality of competitors and team mates.
i do not think that total yards, total completions, total touchdowns, total hits, total strikeouts, etc.. mean much in terms of quality. they do speak on quantity however.
now, as for my pick for best running back of all time.... barry sanders.