On Wednesday,
The chart below, which looks at the career hits, by age, of the three players with 4,000 career hits, suggests that Ichiro's 4,000 career hits actually compares quite favorably. In fact, his time in Japan may have actually hurt his total (see explanation below the chart)...
Data via Baseball-Reference.com
Both Ichiro and Cobb started their careers at age 18 with Ichiro joining MLB at age 27. By the age of 27, Cobb had 1,600 career hits, 322 more hits than Ichiro at the same age. In Rose's first five seasons, before turning 27, he had 899 hits, 46 more than Ichiro during the same age span.
In other words, Ichiro was not putting up crazy numbers in Japan. In fact, he collected fewer hits, in large part because the NPB played just 130- or 135-game seasons at the time while Rose played 162-game seasons and Cobb played 154-game seasons.
However, in Ichiro's 13 seasons in MLB, he has collected 2,722 hits, the most ever in a 13-year span. In the 13 years after turning 27, Rose had 2,658 hits and Cobb had just 2,300 hits.
Ichiro doesn't get credit for the 1,278 NPB hits in the MLB record books. But it is easy to see that if he had started his career in MLB at age 18, he would still have 4,000 hits, and probably more.