yea one of the best american songwriters ever

accidentally like a martyr is one of my all time favourite songs, top 10 stuff.

my fave albums by him are the live album Stand in the Fire & prob Excitable Boy. but he's got a host of great albums really.
the wind is p special. he was never the most prolific but when he learned he only had so long to live he got cracking & made a really stunning final album. at times it's gutwrenching & other times just play rocking.
he had a sense of humour that you don't really get in rock music. or at least great rock music like his. there are a few sarcastic guys lyricist but none are as good a songwriter as zevon was.

but perhaps my all time best zevon moment is his cameo on the larry sanders show & larry makes him play werewolves of london when he really doesn't want to.

this is a fallacy.

as is the idea most other bands' fans don't care about the setlist. (& it's not just GnR who have hardcore fans who go to multiple shows. *tho GnR are a special case because it's been p much the same setlist for 11 fucking years now, not just night to night on a certain leg!!)

they don't HAVE to adhere to that policy, they choose to. they choose the safety of it.
people are paying for a show. it's the performers decision as to what the show will entail. it's not up to the punters to demand the hits.

i didn't know that re: sales figures.
i don't know if that's entirely correct re: enduring on radio. i must confess i don't much listen to radio but when i do i think i'm more likely to hear GnR than Zeppelin, over here at least. or when i'm out a bar or a club i'd defo hear GnR more regularly than Zep, i mean SCoM is still a staple, i don't think that's true of any Zep (tho i concede your point that they've a larger selection of material from which to select). i hear more vintage stones even than zeppelin tbh.

re: influence
well that's a sticky subject. it's an unfair one to make i think. for one there's plenty of influential acts i think are shite so i dunno what it really has to do w/the debate. secondly, yea there's plenty of merit in zep's legacy but it's unfair simply because they went before GnR so you really can't compare on that basis either.
also, GnR were p much the full stop on hard rock - or at least the last mega band from the genre. they in effect ended it. no-one really came after them as there was really nowhere to go: and they couldn't exactly imitate the GnR attitude cause it's almost unique thanks to the nutcase in charge. whereas w/zeppelin, any blues-based band almost ha to go thru zeppelin at somepoint - gnr don't have the same exact frame of reference, it's harder to trace GnR's lineage cause it's so scattershot and all encompassing, zeppelin belong to a more defined territory & and therefore more recognisable in other bands. imo you're argument actually works in gnr's favour as it shows how different & special they were, they were perfect & inimitable whereas p much anyone can follow zeppelin's approach of modifying old blues licks long out of copyright.
(is it also worth mentioning here the cross-gender appeal gnr have as opposed to zeppelin??)

but basically, to go back to the original question & my original point: when you're as perfectly formed as they were '87-'93 it doesn't really matter what else happens or whatever other criteria you wanna hurl at them as an obstacle. it's the quality of the material that makes the case watertight.
i'm not saying zeppelin weren't great it's more than GnR were perfect. & yea they blew it but what they made, what they accomplished, w/AFD & across Lies & UYI put them above p much everyone in hard/classic rock & maybe rock n roll.
if it came down to a debate on just rock n roll i'd maybe take umbrage w/GnR being the best of the best but in terms of classic/hard rock i think they stand that little bit above everyone else.

Slash doesn't need or want a reunion so bad anymore. The balance of power has shifted somewhat.