#3 John Cena's rematch with The Rock is fondly remembered
John Cena played the pseudo heel during his feud with The Rock in 2012. He probably would have even turned completely before WrestleMania 28. Nevertheless, Cena remained a babyface for the "Once in a Lifetime" match.
But had John Cena gone full heel in 2012, a rematch between him and The Rock would have been much more exciting. Cena's first WWE Championship reign as a heel would have ended early so that WWE could transition the belt onto the People's Champion at Royal Rumble 2013.
John Cena could still have won the Royal Rumble Match, but his attitude would be different, and that would add fire to the buildup for the match. Several members of Cena's faction could have attacked The Rock on the Road to WrestleMania. The promo battles between the two legends would have been more heated and memorable.
After defeating The Rock and getting his revenge, John Cena could become even more dominant. This would have forced WWE to build several compelling faces beyond the likes of CM Punk and Daniel Bryan.