|President Monson and his wife|
Slate notes three critical facts about President Monson. He's regarded by 13 million Mormons worldwide as a prophet of God, he was at the center of controversy over the LDS Church's support of California Proposition 8, and has dedicated 10 new temples and announced plans for 16 more during his tenure.
President Monson also was number one on Slate's 2009 list, which you can view HERE. Surprisingly, his predecessor, Gordon B. Hinckley, did not make their first-ever list in 2008. Perhaps it was the controversy about Proposition 8 that made President Monson more publicity-worthy in the perspective of Slate.
To the best of my knowledge, no other Mormons made the list. As of this post, there's been no official reaction from the LDS Church to this story. However, there's an interesting article about President Monson entitled "Mormon Church President Thomas S. Monson's parents prepared him to serve" published on the Mormon Times.
One commenter to the Slate story, Darv Pamela Andersen, thought it was ironic to lump Thomas S. Monson and George Soros on the same list. But the list is merely of the most influential octogenarians, not necessarily the most righteous.