GROOVE and story, something that makes d moment shine.
i have to say GROOVE again! i think that alone makes d difference between a good and a bad solo. eventhough it has bad tone, bad notes, bad sound, bad amps, bad story, bad whatever... it still has some sort of musical value, if it's grooving. that's d effect of a 'sound in time'. d phrasing should make sense of course.
Art is something that u don't completely understand, if it's too obvious it's not art!