No matter how many flashy licks and lines you know, being musical is more fundamental than being technical. The term “phrasing” is used to describe a player's musicality. Great phrasing is the most important element of a solo—even more important than the notes.
The evolution of pentatonic playing comes from early blues, and the sound of the blues started with singers. Singers sang pentatonic melodies, embellishing them in different ways every time they performed. Blues also grew out of the gospel music tradition where improvisatory flourishes were part of the genre—you were expected to sing something different every time. The goal for many rock and blues players has been to emulate the human voice and its improvisatory style. The great rock and blues guitar players all have one thing in common: They have a vocal-like approach to their solos.
Just listen to some great vocal music. The first thing to understand is that singers have to pause to breathe. Guitar players are notorious for playing with no break in the sound, and beginning players are especially guilty of this. Vocalists can't do this, because they must stop to breathe.
Naturally, vocal solos are broken up into small phrases of three or four seconds of music.
Learn every solo you can—this is how you learn to play music. If you're unsure of where to start, the blues is a great place to begin. B.B. King's solos are a great tool for learning the blues style. Many of his solos aren't overly technical and are easy to learn. In rock music, Carlos Santana never fails to play a great solo. While he doesn't rely completely on the pentatonic scale, he uses it a great deal. These are just two examples you can use to get started.
Listen to the guitar solos of B.B. King, Albert Collins, Buddy Guy, and Clarence “Gatemouth” Brown. They all play short phrases and take musical breaths just like singers do. When you improvise, try to leave a little space every few seconds. Breaking up your solo into little parts makes the music easier for the listener to digest.
The vast majority of listeners can't appreciate the technical merits of your solos. They can't comment on how hip it was to use the B-minor pentatonic scale. All they can hear are the phrases you create. As a great teacher of mine once said, “Rests are the windows of music.” Let the light shine in!