This is a comprehensive Oscar site, w/ winners and losers in every category. Scroll to the bottom for winners by year and decade.
http://www.filmsite.org/oscars.html
Browsing those lists, these are some movies that I think had best picture written all over them, regardless of whether they actually won or if they deserved to win or lose.
1967 - The Graduate (L)
1972 - The Godfather (W)
1974 - Chinatown (L)
1975 - One Flew Over The Cuckoo's Nest (W)
1978 - The Deer Hunter (W)
1979 - Kramer Vs. Kramer (W)
1982 - Ghandi (W)
1983 - Terms Of Endearment (W) - loads of noms
1984 - Amadeus (W)
1990 - GoodFellas (L)
1993 - Schindler's List (W)
1995 - The Bridges Of Madison County (L)
1997 - Titanic (W)
1998 - Saving Private Ryan (W)
2005 - Munich (L)
Some disses that I can see are Tatum O'Neal beating out Linda Blair for best supporting actress in 1973. Let's see Tatum rotate her head 360.
The Towering Inferno got a best picture nomination in 1974 -- lame (ask OJ).
Marathon Man didn't get a best picture nomination in 1976.
An Officer And A Gentleman not getting a nomination for best picture in 1982.
Silkwood no best picture nomination in 1983.
The Color Of Money no best picture nomination in 1986, another Scorsese snub.
Working Girl DID get a best picture nom in 1988 -- horrible.
Almost Famous got no best picture nom in 2000 (
Gladiator won that year, so not a strong year).
Cast Away got zero nominations of any kind in 2000. Don't know why
Crash won last year, don't know why I seem to be the only one who hates it and finds the coming to grips w/ racial differences theme utterly played out (
Grand Canyon, Do The Right Thing, Falling Down, A Time To Kill, Higher Learning, etc).