because Res Evil 6 strays away from the traditional zombie outbreak at times to make you fight things like giant monsters just so they can say they 1 up'd Nemesis or RE 4s Ogres.
By claiming that it is better in the story department you are just dead wrong. The premise is good, but the overall execution is terrible. What should have happened was they focus on a single character, like Chris, Leon or Claire and then bring in the other characters over the course of the storyline. What happened instead is we had 3 fractioned storylines, only one of which was actually worth playing.
Not to mention how the checkpoint system in the game is ridiculously flawed, putting you back quite the distance should you "die", despite you just reaching a checkpoint.
But if you like the game then good for you. I just recommend Revelations over 6 as it actually feels like Res Evil game.