In 1949, Yamauchi took over Nintendo after the previous president, his grandfather, had a stroke. He had to leave college to do so, as he was only 22 years old at the time. In those days, Nintendo was a playing card company (as it had been since its inception in 1889). After assuming the presidency, Yamauchi began manufacturing American-style plastic playing cards. These were a big hit, but the market was limited because standard playing cards were associated with gambling, which was largely illegal at the time. However, after inking a deal with Disney to produce family-friendly card games, Nintendo became the #1 playing-card company in Japan.
Excited about this success, Yamauchi traveled to America to visit the American Playing Card Company. However, he soon discovered that the playing card market was very small. Nintendo would have to branch out if it wanted to continue to grow.
Soon after, Yamauchi began to try new products. Some of these included instant rice, a taxi company, and a love hotel that rented by the hour (yes, that's exactly what it sounds like). These ventures brought Nintendo as close to bankruptcy as it probably has ever been. At least until Yamauchi discovered Gunpei Yokoi, one of the Nintendo's engineers.
Around this time, electronic game systems that could be connected to TVs began to crop up. Atari and Magnavox began selling gaming systems to the general public. Nintendo originally signed a contract with Magnavox to sell the Odyssey console. Later, Nintendo created its own system, the Color TV Game-6, a small console with 6 games built into it (although, to be fair, it was really just 6 variations of Pong).
Yamauchi decided it was time to branch out into the American arcade market. Nintendo released some of its Japanese arcade hits, such as Radar Scope, Sheriff, and Space Fever, in America. However, they did not catch on as they did in Japan. Nintendo struggled to gain a foothold in the American arcade market until Yamauchi discovered Donkey Kong, a pet project of future legend Shigeru Miyamoto. Nintendo converted some of its Radar Scope machines into Donkey Kong machines, and the quarters began rolling in. Combine this with the success of the Game & Watch series (also a creation of Yokoi), and Nintendo was fast becoming a household name.
But the best was yet to come. Nintendo then released the Famicom (short for Family Computer). It was an unprecedented success. It was the best selling console of its time, catapulting Nintendo to the top of the video game pile. At the time, video games (especially in America) were largely low-quality and highly expensive. The market was collapsing. At least until the NES was released. Nintendo single-handedly revitalized the American video game industry and left an indelible mark on the medium as a whole. It's not unlike Mario smashing through a level after eating a Mega Mushroom. NES titles were hand-picked by Yamauchi himself, which let to a large number of excellent games, and relatively few poor ones.
Nintendo did not rest after the NES was released. They developed and eventually the Super NES (Super Famicom in Japan) with another round of exceptional games. Super Mario World, Star Fox, and Donkey Kong Country set the bar so high, only Sega and its Sonic games were even close to matching Nintendo's success. Strangely, Yamauchi was adept at identifying good games without ever playing them (a quality which many in the industry do not possess today, even after playing the games). The Nintendo train rolled on.
In what is perhaps a dark spot in Nintendo's history, the Virtual Boy was released in 1995. The product itself was still being developed by Yokoi, but Yamauchi believed it was ready. It was not, and the product was a flop (although it had a some excellent games). Yokoi left the company in shame.
Later, Nintendo released the GameCube. It was a powerful machine, with a significant graphical upgrade from the N64. Yamauchi set the price very low (especially compared to the PS2 and Xbox) to entice customers. Strangely, Yamauchi also purposely made the system difficult to program for. The idea was to keep untalented third-parties off the system, and thus make most of the games high-quality. Unfortunately, this backfired, leading to many poorly-coded games. This allowed room for Sony and Microsoft to cement themselves in the market. That's not to say there weren't any good GameCube games, because there are many. MarioKart, Pikmin, and Resident Evil 4 are just a few of the wildly successful games for the GameCube.
Yamauchi resigned shortly after the GameCube was released due to his age. Satoru Iwata (former head of HAL Laboratory) assumed the presidency and remains there to this day. Yamauchi declined his pension because he felt that Nintendo could put it to better use. However, he retained a 10% share in Nintendo (and subsequently made a fortune when the Wii and DS were released). He also bought the Seattle Mariners baseball team, which opened the door for Japanese players to come to America. The Mariners made their first profit in years when they acquired Ichiro. Yamauchi never attended a Mariners game.
Yamauchi was a visionary, no doubt. He transformed a small playing card company into perhaps the most important video game company in the world. He led a major company for over fifty years. Most people nowadays don't come close to 50 years in a single company. He helped provide the memories we all had as kids playing Nintendo. And his legacy will live on. 1-Up to you, Yamauchi-san.