With The Wolverine & First Class 2 coming up, this would make the X-Men franchise the longest running comic book franchise in history?
Up to 7 movies with these two, I think the longest before was the original Superman franchise (1-4, Supergirl & Returns, 6 movies).
Actually, it's Batman. Counting LA movies only:
The Batman 1943 Lewis Wilson
Batman 1966 Adam West
Batman 1989 MIchael Keaton
Batman returns 1992 Michael Keaton
Batman Forever 1995 Val Kilmer
Batman & Robin 1997 George Clooney
Batman Begins 2005 Christian Bale
The Dark Knight 2008 Christian Bale