I was wondering the same thing and think Spencer may be right that Bobby Thompson going yard off Branca may be the standard bearer (I ever tell the story about meeting Branca at the track while wearing a Giants cap?) as it was the climax of a 3 game playoff with the Dodgers, then more akin to the Cubs as far as a team that always found a way to lose in the end, finding a way to lose in dramatic fashion. Willie Mays in the on-deck circle as a rookie and all that.
The big argument 2011 has it involved both leagues though & likely deserves bonus points that both leagues had epic collapses as well.. Although it didn't have the teams playing head-to-head.
Other candidates:
* '64 - epic Phillies collapse sealed on final day. NYY win by 1 game but clinched day before.
* '07 - Phillies pass Mets on 9/30, streaking COL wins & ARI loses on 9/30 to force 1 game playoff for WC - COL wins & goes onto win NL
* '78 - Bucky "F'ing" Dent - Yanks finished 6-1 only losing game 162, BOS closed 8-0 to force the Dent game - both 99 win teams
* '62 - Giants win #101 on last day, Dodgers lose forcing 3 game playoff which SF wins.
I'm not positive any of these were clearly "better" than yesterday as we often didn't have 2 leagues and 4 games dueling, but I will say many of these were better teams as the Wild Card races this year were 90/91 game winners vs. some of the ones above where they were ~100 & someone was missing...