Because JA added a bunch of flashy lightsaber moves and other acrobatic moves but also nerfed the other things like the movements and the guns. It was a lot more slower, rolling didn't do anything, no more strafe-jumping. Guns were useless now, the Tenloss was nerfed among other things, and saber fighting was dull.
Plus the storyline wasn't as good. Jaden isn't as interesting a character as Kyle. Kyle actually had a backstory and depth to him. What was Jaden's story? He built a saber and wasn't even a Jedi. OMG.
those were just some of the things that i didn't like about it. Other people might add more reasons, but those are all I could think of right now.
It's my ILLUSION!