My vote goes to SUNDAY KIND OF LOVE by The Harptones.

Excellent choice.
The original (?) Fran Warren recording with Claude Thornhill's big band is also worth listening to.
Competition in the doo-wop ballad genre would have to include "I only have eyes for you" by the Flamingos.

Anything by the Ravens. I don't know too much doo-wop but I love that bass voice.
So, "My Baby's Gone" by The Ravens is the best for me.
What about"Sh-boom" by The Chords? Does that count? "Life could be a dream ...."

any picks from this lot of doo wop compilations?
I've got some download credits to use, good steers gratefully accepted