4. The Undertaker's StreakEasily the longest storyline on this list, although the WWE themselves didn't begin to acknowledge the Undertaker's undefeated WrestleMania streak until his defeat of Edge at WrestleMania 24. Quite simply, his run is the most staggering record in professional wrestling history, stretching from his squash of Jimmy Snuka at 'Mania 7 to 2014's heartbreaking defeat at the hands of Brock Lesnar. The Undertaker's once-in-a-lifetime gimmick always makes for intriguing feuds, leading to some interesting WrestleMania clashes whatever the opponent, but the streak really began to take on a life of its own around the time of that Edge encounter. Every bout since had a powerful story attached to it, with the streak becoming a far bigger prize than even the WWE Championship. Defining Moment: The pair of matches against Shawn Michaels at WrestleMania 25 and 26. The first is generally regarded as the slightly better bout, but the storyline leading to their rematch was exceptional on many levels: Michaels' desperation, Undertaker's unwillingness, HBK's heelish actions to secure a match, and the Deadman finally retiring him on the grandest stage of them all.