The 67-year-old actor spoke to "Good Morning America" recently about the fact that the fourth installment was the only film in the franchise in which he was not involved, said the Hollywood Reporter.
"Thank God," Schwarzenegger said, adding, "It sucked."
His schedule as California governor had kept him from filming scenes for the 2009 McG-directed film.
As far as the first three films in the franchise, the actor explained that he enjoys them all for different reasons and would be unable to pick which is best.
"Terminator Salvation" starred Christian Bale and Sam Worthington.