It's very difficult to be original in this day and age. Whether we're talking about gameplay or story, whatever you think up, chances are that someone else thought of it already. That doesn't mean developers (or anyone who wants to create something) should just stop trying, but they should focus on original/unique renditions and adaptations of existing ideas and from that they (and us, the players) might end up with something quite interesting.
Now, in terms of losing interest in gaming, I guess it depends on what draws you to playing a video game in the first place and if and how it changes as you grow up. For example, when I was a kid I used to play games that had primarily fun gameplay (games like The Lost Vikings, The Incredible Machine, Wolfenstein 3D...), then I switched to primarily playing RTS games, Point and Click Adventures, Action Adventures and Shooters (Warcraft 2, Starcraft, Grim Fandango, Monkey Island, Soul Reaver, Max Payne...) - this is when I started getting interested in the story just as much as the gameplay. Nowadays I'm nearly 25 and I primarily play games that have an interesting story, whether they are RPGs, Action Adventures, Shooters, or whatever. I also play a fighting game every now and then, as well as a racing game. I'd say I'm excited about gaming as much as I've ever been, only the reasons have changed.