Slash is a great guitarist with an extemely recognisable style.... but Hendrix wins hands down. You also have to remember that Hendrix had very basic gear by todays standards, so his sound may be more raw but his abilities and originality for the time were way ahead of the curve. Slash is a good guitar player but he is no virtuoso, unlike Hendrix who inspired many modern greats including Steve Vai, Joe Satriani and Yngwie Malmsteen.