1900-1909 Crayola Crayons
1910-1919 Raggedy Ann Dolls
1920-1929 Madame Alexander Collectible Dolls
1930-1939 View-Master 3-D Viewer
1940-1949 Candy Land
1950-1959 Mr. Potato Head
1960-1969 G.I. Joe
1970-1979 Rubik’s Cube
1980-1989 Cabbage Patch Kids
1990-1999 Beanie Babies
2000-Present Razor Scooter
Here are the details from Forbes, including other notable toys of each decade. (Article is from 2005.)