Well I find it very difficult to choose the best version of it.

KD Lang just gets my vote

Il Divo do a very nice version of it.

I also like Rufus Wainrights version

I also Like Alexandria Burke's version. She has a great voice.

I wonder what Ricky Nelson would have been like doing this.

Here you go, listen to all of them on this link

http://www.mirror.co.uk/celebs/news/2008/12/15/hallelujah-from-alexandra-burke-to-jeff-buckley-listen-to-the-top-ten-versions-of