Almost all guitarists know and use the major and minor pentatonic scales, and a lot usse the blues scale too. Most guitarists use the major and minor scales either from knowing the scale or just playing by ear. Many intrumental guitarists utilize modes, but most mainstream musicians just use the major and minor scales.

Take Metallica's black album for example, most people know what their songs sound like. They use minor pentatonic a LOT, as well as the natural minor scale, and the phyrgian mode. BB King plays mainly the blues scale, but he plays some Dorian elements sometimes too. Clapton uses mainly major and minor pentatonic. Eric Johnson uses a lot of Pentatonics, as well as major, minor, and dorian.

The chords people play over affects their sound a lot. For example, a lot of blues players will play the blues scale over a major progression.

My suggestion: learn the seven modes of the major scale and the major and minor pentatonic scales. This will keep you busy for quite a while, and it will give you a pretty good toolbox from which to draw forth the particular sounds you're looking for.