Sorry, for guitarists you need to be talking about what you like in a guitarist before you can qualify one as better than another.
Let me start this by saying [Poor language removed] off Noel Gallagher as a guitarist. Painting by numbers is harder than what he plays. He IS a talented songwriter though no doubt but in terms of guitarist talent, let's not go there.
I always look at things from a metal perspective but not exclusively so.
For sheer technique and taking playing the instrument forward I'd have to say there are 2 guitarists that are pretty hard to surpass (although they are not alone in this lofty category).
1. Joe Satriani
[media]http://uk.youtube.com/watch?v=zzQb79IhoRE[/media]
[media]http://uk.youtube.com/watch?v=sBLVYOFTaTU[/media]
[media]http://uk.youtube.com/watch?v=srZ969GALVg&feature=related[/media]
2. Steve Vai
[media]http://uk.youtube.com/watch?v=EDSxMCmzGjk[/media]
(you could squeeze Malmsteen in here as he plays neo-classical which the others don't, but he is a widely acknowledged **** so I've left him out)
[media]http://uk.youtube.com/watch?v=vTEYD1u8G4Y[/media]
For sheer funk and writing good hooks for me personally it would be :
1. Joe Satriani
2. Angus Young
3. Stevie Ray Vaughan
4. Albert King
5. Ry Cooder
6. Dimebag Darrell
And for just being a great songwriter and using the guitar as a instrument to convey feeling, emotion or a thought :
1. Joe Satriani
2. Dave Gilmour
3. Eric Johnson
and many others spring to mind but these top my list
BTW Whoever said Vai can't write a decent track, here is probably one of the most recognised and well known tracks of the 80's written by the great fiddler himself :
Steve Vai - For the love of god.
[media]http://uk.youtube.com/watch?v=5NfZBvRvkIg[/media]