6. Prince Of Persia
Parkour gameplay may now be the domain of Mirror's Edge, Dying Light or Assassin's Creed, but once upon a time it was a unique aspect of the Prince of Persia franchise. Some might feel that Ezio or Bayek are now far more iconic than the titular Prince, but he was around long before any of the assassins showed up.
With more of an emphasis on style and a greater focus on action and combat, Prince of Persia has many entries that are fondly remembered by fans, but the money spent on the reboot for the seventh generation of consoles just did not match up to the runaway success of the Assassin's Creed franchise. Being similar in focus and gameplay, this was kind of a kiss of death for the Prince.
The main problem is simply that we don't know where we stand with the franchise. Back in 2013, studio head of Ubisoft Montreal Yannis Mallat said the series was "paused", and then in later months, Ubisoft said they were planning next-gen entries in several franchises including Prince of Persia.
Sadly, it's been five years since that comment, and we're yet to hear or see anything new.