http://www.corfid.com/gl/press/press04.htm
That's a review from a music critic which covers both Gord's strengths and perceived weaknesses. There are other reviews and articles. Try a Google search under ["Gordon Lightfoot" +critics] - without the brackets - for more sources.
As for influences, there's some country in early Lightfoot (and his guitar picking is 'Travis' style, as in Merle Travis). He came in about midway to the Great Folk Revival of the 60s, and sang a number of traditional folk songs, especially with Terry Whelan (with whom he formed The Two Tones)before he began concentrating on primarily writing his own songs. He is a huge admirer of Bob Dylan (and I believe the sentiment is returned) but since the 60s his music has been really his own style.
He's disciplined, hardworking, modest, and I'd guess shy - the quintessential Canadian.