The Assassin's Creed series became an instant hit upon its debut nearly 20 years ago and has managed to maintain that status all the way to the present day, with only a few occasional dips. There are 14 main games, but when you include spin-offs, VR titles, remakes, and other releases, the total exceeds 30, and this means the series has sold an impressive number of copies.
In a press release from Ubisoft, they write: "Since it first launched in 2007, the Assassin's Creed series has sold more than 250 million games worldwide. The franchise is now established as one of the best-selling series in video game history."
At least two of those 250 million come from Assassin's Creed: Black Flag Resynced, which sold two million copies on its very first day, so it seems safe to say that the series' popularity is going strong.