Sequel-itis: when everything in the original movie’s been endlessly overexposed.
Alien sequel-itis: We know when the alien opens its yap out comes a tongue that has teeth on it, and it bites people’s faces off. We’ve seen that too many times now. That’s not scary anymore.
Predator: We know when a predator starts fiddling with its prehistoric glyph LED 2-way wrist-radio, something’s about to go boom! Yawn.
What do we know about “Terminator” movies? When the T-1000 model terminator gets shot in the face, it will grow its face back immediately. Double yawn.
And we definitely, definitely, definitely know that Ah-nuld will tell someone “I'll be back.” It once carried humorous dread; now it’s a seriously tired running gag.

(L-R) Christion Troxel, John Edward Lee, and Luke Sexton stand behind CGI Arnold Schwarzenegger terminator, in "Terminator Genisys," from Paramount Pictures and Skydance Productions. © 2015 Paramount Pictures/MPC/Paramount Pictures