Greatest Songwriter of all time

I was reading the Dylan post and it got me thinking. There are many great songwriters that come to mind, my expertise/knowledge is primarily with rock music. If you could only pick three, what would they be? My vote for best lyrics goes to:

Jim Morrison
Bruce Springsteen
Elvis Costello

Best music goes to:

Mark Knopfler
Stevie Ray Vaughn
Frank Zappa
of course bob and bruce rule. i'm surprised,tho, that no one's put any female singer/songwriters on their lists (but for joni mitchell). how about: carole king, ani defranco, shawn colvin, iris dement? and on the male side, how can pete seeger, jackson browne, james taylor, warren zevon, loudon wainwrigth III and greg brown be left off all the lists thus far? -cfb
Lou Reed, Bob Seger, Steve Winwood, Bill Quateman, Richard Thompson, Susan Vega, Bonnie Raitt, Joni, Grace, 'n on 'n on... God I love this hobby...