Shinya Takahashi, President and GM of Nintendo Entertainment Planning and Development (EPD). Basically, he's the big boss of ALL software produced by the company, signing off on just about every game the Big N publishes. Takahashi started out working under Miyamoto in the late 80s and throughout the 90s, mostly working on the technical side of things like Motion Capture and 3D engine development. When Nintendo restructured it's R&D departments in 2002, Takahashi was transferred to the newly created SPD division, led by Satoru Iwata himself. His first job was serving as Producer for the Brain Age series. Somewhere around 2010, Takahashi was promoted to Head of SPD, giving him a similar role to Miyamoto over at EAD.
Shinya Takahashi has a different philosophy to approving games than Miyamoto does. Miyamoto focused on instilling his philosophies and approach to game design in lower rank staff, so that everything has a cohesive style. Takahashi however, focuses more on cultivating a developer's unique individual talents. A good example at the difference between the two would be EAD's Wii Play, and SPD's Wii Play Motion. Miyamoto gathered a single team within Nintendo to create multiple games to demonstrate the Wii Remote. Takahashi on the other hand, called up 5 or so outside studios to make a bunch of games that had their own unique identity, while still keeping a cohesive style. Miyamoto always focused on trying to cast a wide net with a single title, Takahashi however feels that each game should have its own mission, and its success should be based on how well it accomplishes that mission. Takahashi has green-lit games that while not having a ton of commercial success, still helped bolster Nintendo's overall lineup.
Despite his high position at the company, he's been kind of under-recognized by Nintendo fans. Some people still think Miyamoto is the one who calls the shots, when Takahashi has explained that he's more of a creative advisor now than a decision maker. He'll look at projects and give his opinion, but he's not the one who approves the budget or signs off on ideas. All that stuff is handled by Takahashi. Nintendo's been trying to push him into the spotlight more recently, having him co-host Nintendo Direct episodes alongside Koizumi, so hopefully with time, he'll become as beloved of a figure head as Miyamoto or Iwata.