I can agree with the continuity issues going from the 2000s films to the prequels, but not the alleged continuity issues between the prequels.
-November 1962, X-Men First Class ends with Magneto freeing Emma.
-November 1963, Magneto is apprehended while trying to save JFK in Dallas.
-March 1965, Banshee and Havok are drafted and sent to Vietnam. Banshee is KIA.
-At some point between '64 & '72, Emma, Azazel, Riptide & Angel Salvatore are captured by Trask and Stryker and killed for experimental purposes. Mystique is the sole survivor of Magneto's crew.
-January 1973, Wolverine arrives at Xavier's School and the plot of DOFP unfolds.
-DOFP ends with Mystique posing as Stryker to save Wolverine from Stryker's experiments
-At some point between '73 and '83 Stryker captures Wolverine or Wolverine volunteers for Weapon X.
So again, where are these continuity issues everyone's obsessed with?