Like comic books and television shows, a good rivalry can keep a good video game franchise going for years. Or decades if you're the Super Mario Bros.
Scorpion Vs Sub-Zero and later Quan Chi
If you remember the early Mortal Kombat games, Scorpion was after Sub-Zero for killing his family and clan. After over a decade, the story has been changed and it wasn't actually Sub-Zero but Quan Chi. Quan Chi actually used Scorpion's hatred for Sub-Zero to control Scoprion. Scorpion spent years hating the the wrong person. But before Scorpion found out, he killed Sub-Zero thinking he avenged his family. In Mortal Kombat X, Scorpion finally avenged his family correctly by killing Quan Chi. Unfortunately, that death started a chain of events that almost destroyed the world. Thumbs up, Scorpion.
Ryu vs Sagat:
Sagat was the king of the hill until he went up against Ryu. Ryu won the match but also left Sagat with a giant scar across his chest after hitting him with his dragon uppercut. This scar was constant reminder of his loss to the up and comer who would later be recognized as one of the greatest fighters in his world. Sagat would spend time recovering and refining his skills to beat Ryu for scarring him. Eventually, Sagat found piece and turned his hatred for Ryu into respect.
Mario and Bowzer:
Since 1986, Mario has been going from castle to castle battling his arch nemesis Bowzser and later on fighting his crazy dinosaur/dragon kids all to save Princess Peach (or is it Toadstool?) who still doesn't have the foresight to upgrade her security so she doesn't get captured every two days. That said, Bowzer is just an ***hole. Seriously, why does he keep stealing the princess? Ransom? Doubtful. Anyone can get coins in that silly kingdom. On top of that, Bowzer lives in a castle and owns TOOOOONS of land. He literally has castles in every territory. So why does he do it?Beastiality? Most likely.
Kratos and the Gods:
Kratos is easily one of the most hate filled video game characters ever created. Although, Kratos has a legitimate gripe against the gods. Since birth, he was destined to become an angry killing machine. His brother was taken from him by the gods. Ares tricks Kratos into killing his wife and daughter so he Kratos could lose that one thing holding him back from being unstoppable. And after Kratos killed Ares as he was instructed to by the gods, Zeus wanted his son Kratos dead before he could eventually kill him like Zeus tried to kill his father Kronos. Kratos may be a d***, but his anger is justified. Also, I wouldn't be shocked if Zeus raped Kratos' mother. Zeus is a known rapist.