Jeff Lynne got way more mentions than David Bowie....?!?
Whilst I like ELO, am I missing something here? Is it the Tom Petty connection?
Coming from a somewhat limited veiwpoint, I'd include Lennon / McCartney (probably as one entry [i.e. within The Beatles]), Tom Waits, Springsteen (not latterly!), Billy Joel, Chuck Berry (probably more the influence of his songs than the actual songs), Queen (I know!!), Paul Simon, Bowie
Couldn't put Roger Waters in there (much as I'd kind of like to - his best stuff was within Pink Floyd)
Elvis Costello
Neil Young (respect his art, his attitude, got loads of his stuff [hard to keep up with], love Harvest, Freedom, and others - but I'm not sure he ranks as highly as a songwriter - does that make sense?)
Buddy Holly - hard to say - I know he's credited on quite a few tracks, but how much came from him. Again, the songs and his legacy are high up there, but whether he can be considered as a brilliant song-writer...?
Lou Reed
Paul Weller
Leonard Cohen
Prince?
There are plenty of others who I'd possibly include if my tastes were wider, particularly Joni Mitchell, Kate Bush?, Tori Amos (keep meaning to listen beyond the first two albums!).
Like most of these things, it comes down to how strictly we're defining 'songwriter' (not strictly, and that's fine); personal choice and experience; age and influences; preference of lyrics over tune, or vice versa; whether you consider an artist's influence as part of their greatness, etc.
Dunno if this'll suffice to kick-start this thread (or whether there's any point doing so?) - any decent songwriters appeared in the last 5 or 6 years?? [I'm sure there have been, but maybe not of the longevity or calibre of some of the above].