#3 Brock Lesnar vs Roman Reigns
Back at WrestleMania 31, Lesnar and Reigns fought for the WWE Championship in the main event. The match was better than anyone expected, and even though the match ended up with Seth Rollins on top (thanks to his cash-in), Roman came across like he could hold his own against The Beast, and proved his potential for being the top star.
Many expected them to face-off again soon to conclude their rivalry, but it wouldn't be for another three years before they had another one-on-one championship clash, this time for the Universal Championship at WrestleMania 34.
Like the dream match for the WWE Championship, WWE had a story prepared for the Universal Championship as well. They could have booked it as Roman finally getting to complete his unfinished business by defeating The Beast.
The victory would have also felt sweet, and would have made Roman look stronger, especially after Lesnar's tedious run with the belt. But contrary to what fans wanted, Brock dominated most of the match, and Roman lost cleanly.
Roman did get the last laugh at SummerSlam, as he defeated Brock, but the damage was already done, because after the WrestleMania defeat, Roman lost his credibility as a main-eventer, and thus no one really cared for their match at SummerSlam.