Awesome guitarist.
Awesome song-writer.
Awesome musician.
For mine, he was what made Queen rock. I've got all his solo albums, all of Freddie Mercury's solo albums, and half of Roger Taylor's albums. John Deacon never released any solo albums. Anyway, my point being that I can compare all their music styles to eachother. Freddie mostly brings the melodies; Roger and John, the depth (especially since about 1985 onwards); and Brian May, the rock.
They can all rock, they can all create awesome melodies, ect; but Brian May definately 'rocks' more than the others combined.