Satoru Iwata, who as chief executive of Nintendo oversaw the introduction of gaming systems such as the Nintendo DS and the Wii, died on Saturday. He was 55. He was the first chief executive to come from outside the Yamauchi family, which founded the company in 1889 as a manufacturer of playing cards and ran it until Mr. Iwata was appointed. At the start of Mr. Iwata’s tenure, Nintendo, long a leader in home gaming systems, was fending off fierce competition by rivals like Sony and Microsoft. Under his watch, the company surged ahead with the release of the Nintendo DS, a hand-held gaming system, the popular Wii home gaming console, and Amiibo, a line of interactive toys.