Usually his own versions. I do like Peter, Paul, & Mary's versions of Early Morning Rain and For Lovin' Me, but I like Gordon's redone versions of both songs the best (from the first Gord's Gold album). His original versions of both of those songs are a little too "country" for my taste (I don't hate country music, but I'm not particularly fond of it - so it's a matter of personal taste).
I like the Cowboy Junkies "The Way I Feel" and Bruce Cockburn's slower version of "Ribbon of Darkness" on the Beautiful tribute album. Sarah McLachlan did a very nice job with "Song for a Winter's Night" on her album Wintersong.
I love the covers I hear every January at the HUGH'S ROOM tribute shows.. and Gordon loves them too! so many great artists putting their own spin on the tunes...(use search engine here for HUGH'S ROOM and you will see many videos over the years.. including Gordon's daughter Meredith singing a couple of her dad's songs)
But no one sings a Lightfoot song like The Man himself..
I prefer Tony Rice's bluegrass versions of "Sixteen Miles", "Walls", "You Are What I Am" and "Go My Way" to Gord's originals, but it's probably because they were recorded years later with more modern equipment and production standards.
My wife prefers Quartette's all-female version of SFAWN to Gord's. I say nobody does it better than Gord (and I say that about all the other songs he's written.)