try to stop thinking of scales and patterns on the guitar when improvising. just listen. i bet you have heard millions of melodies in your life that where great in your ears. so just try and produce such melodies on your own. it sounds harder than it actually is. have you ever sat infront of the radio and listened to a song, and in your mind there was some sort of melody going on that seems to fit perfectly over that song.
sometimes i find myself in that situation and i think to myself "why didnt they do it that way? it would sound much cooler" - that feeling is what i use when i improvise. i know it sounds pathetic and it has been said millions of times on this board, but you gotta develop your [musical] ear. when you improvise YOU are part of the song. your feelings are transported through the notes you play. you can imagine, that there i no use in thinking of scales and patterns in that situation.