Watch the Strategy 5: Engage Your Audience online guitar lesson by Jon Herington from Ear IQ: Soloing Strategies
A time-honored way of creating interesting melody - which is what playing a guitar solo is all about - is to use the technique of theme and variation. Classical composers have used this technique for hundreds of years, and it's the basis for most jazz improvisation. There's something about the way it plays with the listener's expectations, sometimes satisfying them, sometimes surprising them, but in the best cases, always keeping them engaged.
Here's a song where I used quite a bit of that. It's a pretty advanced song, harmonically speaking, which is typical for its composer, my good friend and Steely Dan bandmate Jim Beard. Let's check it out.