The British-born actor Mark Rylance has spent much of the current theater season in New York, recreating two acclaimed performances originally seen in London. Last fall, he starred in a revival of David Hirson’s period comedy La Bête at the Music Box Theater and this spring he is appearing at the same theater in a new play, Jerusalem, by Jez Butterworth. Reflecting on these two performances, Charles Isherwood wonders whether Mark Rylance might just be the best actor of his generation.