I am going to pick Jack Butler Yeats (1871-1957, Sligo) as Ireland’s greatest artist. And yes he was the brother of William Butler Yeats and son of the artist John Butler Yeats, notable in his own right.
Wikipedia offers the following useful description of Jack Yeats:
His favourite subjects included the Irish landscape, horses, circus and travelling players. His early paintings and drawings are distinguished by an energetic simplicity of line and colour, his later paintings by an extremely vigorous and experimental treatment of often thickly applied paint. He frequently abandoned the brush altogether, applying paint in a variety of different ways, and was deeply interested in the expressive power of colour. Despite his position as the most important Irish artist of the 20th century (and the first to sell for over £1m), he took no pupils and allowed no one to watch him work, so he remains a unique figure.
I don’t think there are images I could show to convince you that Yeats should stand above the other contenders. His signature expressionist works are thick with three-dimensional texture, and they look like crap on-line. I am fortunate to have seen a large exhibit of them lately in Dublin. When I first saw some many years ago, I thought they were a splotchy mess, a kind of second-rate Gaelic Kokoscha, but they hold up and improve remarkably well with time. Everything is where it ought to be.
Here is a “more normal” picture by Yeats:
His scenes are more animated, more impudent, more multi-faceted, and fresher than those of any other Irish painter. It is easy to imagine him still inspiring painters today, Irish or otherwise, and I don’t think the same is quite true for the other names surveyed. There is something “whole greater than the sum of the parts” that makes Yeats a clear, easy, and I think (mostly) consensus choice for Ireland’s greatest artist. And he certainly was “Irish enough” to count.
Here is a good Christie’s short essay, mixed in with six high-quality images of works recently up for sale. Oh, and here is one of the expressionist horse paintings after all: