Titan Souls is a pretty solid game, but I can see where it may not gel with some players.  There is quite a bit of difficulty to it as you have to learn each titan's patterns and figure out how to expose and attack their weak points, and others may just see this as a rip-off of Shadow of the Colossus.  If you can get past that, Titan Souls provides quite a bit of challenge, but admittedly could have gone on a bit longer for a $15 price point.