I'm a little confused here because the "Best Moment" and "Most Memorable Moment" aren't the same thing in this situation, at least not for me. The title of the thread is "Best Moment" while poll options lists the "Most Memorable Moment" so it's just not all that cut & dry.
The "Best Moment" was Bryan winning the WWE World Heavyweight Championship and delivering the huge payoff that fans wanted. Considering the ending of the streak, it's also a moment that the fans not only needed, but the show needed it as well. Daniel Bryan celebrating in the center of the ring, hoisting two titles, confetti flying all over the place and leading 75,000 people in a huge "YES!!" chant was a gratifying, feel good moment that was desperately needed.
Now, as for the "Most Memorable Moment", that can't be anything but Brock Lesnar ending The Undertaker's undefeated streak at WrestleMania. The absolute shock rippled throughout not only the wrestling world, but even through the mainstream media. Both Bryan's title win & the ending of the streak got mainstream press coverage, but the streak was the much bigger story. Taker's streak was the Rock of Gibraltar of pro wrestling; it'd withstood the passage of time and came to be viewed by fans as reliable as the sun coming up each morning. People watching at home or in the crowd didn't have the slightest clue how to react save that we were all just flat out shocked. It'll go down as an incredible moment that signaled a true changing of the old guard and one that could have potentially derailed WrestleMania XXX