I've been looking forward to the results of the '70s ballot
This sounds like an interesting idea though, and a Top 25 of any decade will (hopefully) encourage more people to submit a list.
As for recommendations, I have listed below a film from every decade that I think every horror fan should watch. It's not necessarily the best film from that decade, but an essential (and generally lesser viewed) one nonetheless!
Beginning of time - 1929 - L'Inferno (1911)
1930-1939 - Mad Love (1935)
1940-1949 - Dead of Night (1945)
1950-1959 - Dementia (1955)
1960-1969 - The Innocents (1961)
1970-1979 - Messiah of Evil (1973)
1980-1989 - Retribution (1987)
1990-1999 - The Addiction (1995)
2000-2009 - Little Otik (2000)
2010-2013 - Berberian Sound Studio (2012)