Underrated artists

One of my commenters, Carroll Powell, makes a very good suggestion. It's all very well having a go at overrated artists, but it's a lot more use flagging up underrated ones.

His own suggestions: [N]o-one writes better than William Trevor or John McGahern (now, alas, dead). Shameful that neither have won the Booker.I'll return to this theme, but off the top of my head, I'd say that Carl Nielsen deserves to be ranked with symphonic greats, that for all the popoularity of some of Elgar's music, he is nonetheless woefully underrated, and that there has been no finer British conductor than Vernon Handley.

Suggestions, please (in any art form).