Opinion:
j40bob
I looked at their list and it's a strange mix. I guess it depends on your definition of a great songwriter. Do Hunter and Garcia, for example, belong because they wrote a lot of the songs that were performed by a major band? Are the songs really good enough to warrant their admission or was the popularity and artistry of the band bigger than the songs? And there are quite a few on the (very long) list of whom I could ask the same question.
Personally, I think the Songwriter's Hall of Fame should be much smaller and really try to divorce the success of the artists from the quality (and quantity) of the songs.