First off...I feel that there are really four candy holidays, beginning with Halloween. Halloween starts it off, then you get into all of the candies to fill Christmas stockings, then there's everything out for Valentine's Day, and you conclude with Easter and all of the goodies the bunny is supposed to bring.
While I think Christmas and Easter bring the best of the candies to the retail market (Cadbury eggs vs. Hershey's candy cane kisses), when it comes to the secular festivities associated with all of these, it's Halloween for me. Especially since Cadbury has started releasing Halloween versions of their traditional Easter candies.