1. instrumentally, obviously. They are all known for that harmonica brace, acoustic guitar thing. Bruce less so, but he has still done it, and done in front of big audiences. But it goes beyond that. Bob thought Neil's Harvest record stole his sound, and Bruce's current flirtation with the violin sound can be traced to Desire.
2. the ability to speak truth to power in a way that is successful. Young's Ohio and Bruce's Streets of Philadelphia come to mind.
3. their idiosyncratic vocals. Springsteen is a better pure singer--that dude can wail--but they each have a way of delivering a song that is deeply personal, and puts such a strong stamp that covering them is a dangerous business.
4. unkillable. Young should've been a non-entity after the stuff he pulled on David Geffen, but he came back with great albums like Sleeps with Angels. Bruce was never as unsuccessful as Dylan or Neil, but the double release of Human Touch and Lucky Town was a low point from which he really might never have recovered...but then The Rising.
5. dubious relationship with the press/mass media. Dylan sold Times Changin' and Lovesick, and Bruce was co-opted by Reagan with Born in the USA. Inexplicably, Bruce's fans were unaware of his politics when he openly supported Kerry. Neil recorded Let's Roll, which may or may not be jingoistic. When things like this happen to other artists, it doesn't matter. These 3 are lantern lights of dignity and self-control in the sea of darkness that is our celebrity culture.
6. Both Young and Springsteen openly acknowledge their debt to Dylan. Dylan fans may wish they did so more, but we can sometimes be sycophantic in that way. Springsteen did Dylan's induction into the Hall of Fame, and he and Dylan played together on more than one occasion.
That was amazingly wrapped up, and basically everything I needed to say!
Dylan, Springsteen and Young - my favourite artists of all time, probably. Amazing.