Thank you for your response. Actually my i have reduced my action, because the strings were too far from the fretboard. It feels much better to play without applying so much force. I think you're right, the higher frets are damping the string vibration.
I mentioned EMG (passive) pickups because, i once tried an ESP (ESP LTD EC-401) with EMG pickups in a guitar shop and it felt so nice to play, the action was exactly right), and the sustain was awesome too.