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!