It's pretty much everywhere. Movies, TV shows, you name it. A series that runs for x amount of years. Eventually ends in a wimpier. Because of various reasons. The main one being boredom. Yeah, you can make a great game etc. But if the sequel feels like the first entry. People quit. Some people just quit, in general.
A lot of movie franchises see drops in the next movie. Even though people unanimously say it's great. And nothing else is blocking it. Like say Star Wars overshadowing other films. It's the more of the same. Games are honestly lucky. Were they can survive for decades. Without needing a reboot. Similar thing happens in comics. It does take a long time for a refresh to happen.
Brain Training was a pure definition of a fad. I bought the game. Soly because it was being talked about so much. I liked it, yeah. But at the time. We didn't have phones to cater to our needs. I couldn't really watch a movie or a TV show on the train, in 2006, easily. Once that changed. I really dropped all the casual games that people hyped up. Nintendogs I didn't buy. Because, I wanted the sequel during the DS. Not the 3DS. It was one of those games taking way too long, for me. I did the same thing with Donkey Kong. The GC bongo era killed the franchise for me.
