Interesting question about the Best Song Oscar. I wax nostalgic in my review for "8 Mile" (which will go live one of these years, LOL) about the last time I loved all 5 of the Best Song nominees--1970 (for film year 1969). Yes, I'm sure some of you weren't even born yet, in which case you can kiss my ASS. 
I was alive back then but wouldn't say that 1970 had the best fives songs ever nominated.
For Al We Know (Lovers And Other Strangers), Pieces of Dreams (Pieces Of Dreams), Thank You Very Much (Scrooge), Till Love Touches Your Life (Madron), Whistling Away The Dark (Darling Lili)
Madron is a film I've never seen and don't know how the song wks in the film. I think there were other songs that were better.
Three songs that were eligible but didn't make the final cut
"EVERYBODY WANTS TO BE A CAT" - The Aristocats -
"LET IT BE" - Let It Be
"SUICIDE IS PAINLESS" - M*A*S*H -