Persons of the Decade.

[The Mikado]

Why not And I wouldn't be suprised if it has been done before.

1900's
1910's
1920's
1930's
1940's
1950's
1960's
1970's
1980's
1990's
2000's

1900s: Orville and Wilbur Wright
1910s: Gavrilo Princip
1920s: Calvin Coolidge (Embodied the spirit of the era, not for anything he did)
1930s: John Manyard Keynes/Adolf Hitler
1940s: Mohandas K. Gandhi/Mao Zedong (Both, rightly or wrongly, represent the massive post WWII changes in the Third World)
1950s: Joseph McCarthy/Elvis Presley
1960s: John F. Kennedy and Nikita Khruschev, jointly, for averting the destruction of the human race
1970s: Henry Kissinger
1980s:  Mikhail Gorbachev/Deng Xiaoping
1990s:  Tony Blair...just kidding!  Don't shoot!  The Internet, though it isn't really a person.
2000s:  Osama bin Laden

[The Mikado]

1900's: Theodore Roosevelt
1910's: Woodrow Wilson/Kaiser Wilhelm II (tie)
1920's: Eh... the 20s were boring. Coolidge, I suppose, those he's really just representative of them.
1930's: Franklin D. Roosevelt/Adolf Hitler (tie)
1940's: Winston Churchill
1950's: Nikita Khrushchev
1960's: Martin Luther King Jr.
1970's: Richard Nixon
1980's: Ronald Reagan/Mikhail Gorbachev (tie)
1990's: This is difficult... the computer or the internet or something, if that's allowed
2000's: George W. Bush

7 Presidents. Interesting.

Shows a lot about you: namely, Amerocentrism.

I note that Poincaré is the only one of my choices that has not been also used by someone else.

True...

No one's stolen my Gavrilo Princip one yet.

[The Mikado]

Glad to see I'm not the only one sticking up for John Manyard Keynes.