I have long thought that the '07 Pats season was #1 on this list and they will likely never have another chance at a perfect season (although 16-0 reg season still holds up); however, recent SBs have changed my mind. The Butler INT and the ATL comeback were some of the best wins in sports history. I am not saying we didn't deserve those games, but they helped take the sting off of '07 (and '11).
But the more time that goes by, the more I get upset at the 2010 Cs. They had a chance to go up 18-15 in championships to the hated Lakers (I know Minny has some of those and they shouldn't count, but that is not the consensus out there). We were up 3-2 in the series and up with just few minutes to go before it all crumbled apart. It was devastating now and seeing how our current chances are about to go up in smoke, it creates even more disappointment.
I feel similar to the '86 WS as I do to the Pats. The Red Sox have been monsters this century. At the time, it was like the worst thing ever, but time has helped heal those wounds.