A truly innovative idea in gaming is hard to come by.
Much like other art forms, while trends tend to come and go, rarely does a new release have such an impact that it substantially shifts the current gaming meta.
In an industry populated with new and interesting concepts, when a game comes out that really breaks the mould, there are always going to be more unoriginal developers who see dollar signs, and attempt to pump-out a lesser, but similar, release in order to capitalise on a trend.
This is particularly the case when a game happens to capture the imagination of casual players, with rip-off titles hoping that parents wouldn't be able to tell the difference when they go to the shop to buy a present for their nearest and dearest.
After all, while they do say that imitation is the sincerest form of flattery, the majority of these titles do little to praise the source materials they so clearly took a little too much inspiration from.
The history of video games is full of ideas being shared and borrowed, but these titles were painfully poor compared to the original works they so closely copied.