Here's something to think about
You've memorized all the modes like the back of your hand. You can play your major, minor, diminished, and even augmented sweeps cleanly at blazing speeds. You know the fretboard up and down and can name all your keys, relative minors, majors, and dare I say it…You even know the enigmatic scale! You can even play your “Intense Rock” exercises faster than Pablo Gilberto himself…So why are you still struggling to come up with original lines and phrases? Perhaps you aren't thinking creatively when you're improvising. One thing I've noticed about some guitar players when they are improvising and practicing is that they do not attempt to play anything new, they are not creating on their instrument but rather playing things they already know. By doing this, you are not practicing at all and you will not get any better, you are simply wasting your own time.
Whenever you're soloing over a progression, you should think of a melody that would sound good over it and then play that; actually listen to the chords being played and don't simply run up and down the scales because you'll sound like an idiot if you do so. And by thinking of a melody over the chords, I don't mean calculate the number of 16th and 32nd notes you can play at the given tempo. A common misconception some guitar players have is that speed does not equal good. Good guitar playing has a lot more to do than speed; it's about the feel, the knowledge of the fretboard, and many, many things other than speed, it's also about technique. Another misconception about technique is that it's not just speed. Technique is being able to find the right fingerings for certain lines you might come up with, good technique is knowing how to sequence a passage to make it sound unique, technique is knowing how to bend a note or sustain it so that it does not sound like “dead” vibrato. Then again…speed does not equal bad either, when you listen to good guitar recordings such as either of the first two Alcatrazz albums (No Parole For Rock N' Roll and Live Sentence), the obvious thing you hear is a very young Yngwie playing very fast. However, he also plays with such feelings and emotions, it's ridiculous. You have to be able to obtain the ability to distinguish good fast guitar playing from terrible fast guitar playing.
Another way to develop guitar concepts is to learn licks from others. One example is Yngwie Malmsteen (yes, him as another example)…everyone knows, or better know who he is. He claims to have learned every single early Deep Purple song and Ritchie Blackmoore lick along with many, many classical pieces. This is what has enabled him to develop his own voice on his instrument and create a unique sound. Ultimately, what has what made him sound like Yngwie. By gaining a vast library of licks, you are able to feel comfortable with your instrument and improvise with confidence, rather than stumble around and pick at notes within the given key. However, this does not mean you should learn every single song by your favorite guitar hero, but it's good to take your tascam out every now and then and take a gander at what's being played to have an idea of the concepts behind the licks. That's all for me on this one and happy playing.
John Li is currently living in Tampa, Fl, his influences are Uli Jon Roth, Yngwie Malmsteen, and Allan Holdsworth. John aspires to become a guitar hero.