The problem that you probably have (though I haven't heard you play, so I'm just guessing) is that you play the notes, but they don't sound good--I'll trust your judgement on this, too--you probably don't--there is a ton of difference between playing the notes, and getting each of them to sound good--If some of you don't believe me, just go down to the local middle school and ask to sit in on the beginning band class!!

You have to work on the sound. Just sit and play single notes, and try everything that you can think of, starting with all the nice tricks that people have posted, till you get a sound that you like--

You may experiment with the angle of the pick, the thickness of the pick, not using a pick- there may be a little snap that you can use that gives your notes more punch--Then think about the way you are fretting the notes---a little extra squeeze here, and little vibrato there, and your sound could improve overnight!! And be sure to ignore the people who tell you not to be too hard on yourself(and especially ignore the people who tell you not to hold yourself up to people that are really good--If you are going to copy, copy the best!!!)--you are just trying to get better, and, with all of their good intentions, they are discouraging you from following your own good instincts!!!