How many years did Gehrig play? Ichiro been there only 10 years. Take ALL his pro numbers (yes, including Japan) and see where he sits. I’d say he was pretty high.
Also, the position in the batting order is of vital importance. A lead off hitter is supposed to get on base, a clean up hitter is supposed to hit him around. With Ichiro on first, the pitcher has to concentrate on both Ichiro and the batter. That is Ichiro’s job, to hassle the pitcher. Hard to do that sitting on the bench after a homer.
Japan is a minor league. It’s only MLB that counts. I agree leadoff hitters are supposed to get on base, and score runs. Their function is simpler and less demanding than a number 3 hitter, who is supposed to do everything a leadoff does, plus produce runs. The best leadoff hitter of all time is definitely Rickey Henderson. He scored more runs, stole more bases, drew more walks, hit more homers than any leadoff hitter. He’s top dog in that dept.