Maybe it's time to stop
One of the nice things about games is that really, there's nothing that automatically says that the fifth installment of a given franchise is going to be bad. Heck, if a franchise makes it to five installments that's kind of heartening. You don't get that many games on the shelf if the first one was...
The trouble is that every franchise is someone's favorite. I picked three franchises here - including one of my favorites, I might add - specifically to avoid picking on anyone too badly. Sometimes, a certain line of games just doesn't work any more past a certain point. Some ideas get mined out, however great they may be in the beginning. There's a point when you want to say "enough is enough." Of course, the flip side of that is that people buy based on the franchise, which is why Okami - a game that inherited all of Legend of Zelda's DNA while being fresh, original, and unique - sold approximately four copies, one of which was immediately traded in. So I'm well aware of why these franchises will never end, but still. Hope you enjoy!