[MDLW]

Kenny Wayne Shephard covered Oh Well on his 'Live On' album. Not bad.
Better though was Stan Webb's version in the middle of a rendition of his own 'Poor Boy' from 'Stan the Man Live'. Slightly altered lyrics but enjoyable to listen to with a nice little spoken tribute to Greeny just before he plays it.
BBM also did an electric version of The World Keeps on Turning on the expanded issue of 'Around the Next Dream'. Quite a long version with Gary Moore's (RIP) usual Greeny Lite playing but worth a listen. Moore also covered Stop Messin' Around amongst others, aside from the Blues for Greeny album, and Jumping at Shadows, although not a Greeny original of course.
Ian Parker added his version of Green Manalishi to the end of 'Almost Cut My Hair' from his live album 'Whilst the Wind'. Slightly different take on it. I like it.
As far as my favourite cover goes, I'm afraid I would have to go for the obvious and say Santana's Black Magic Woman. It's probably the only Greeny cover that I listen to fairly regularly. As has already been said, most of the covers don't live up to the originals such was his talent as a musician.
Oh for him to rediscover the art of writing again...