A number of pieces of art have had a strong effect on me. All have been ones I have seen in person over the years; being present with the work is so much more overwhelming emotionally.
Among them:
Sunflowers by Van Gogh. The intensity of the colors and the depth of the brushwork were stupendous.
Seeing Guernica before it was repatriated to Spain brought me to tears.
One rainy day I was walking through The Louvre, and stepped into a small side gallery. Right in front of me was Ship of Fools by Hieronymus Bosch. I was stunned, and the beauty and detail left me in wonder.
About seven years ago, my old girlfriend and I went to see an exhibit on 17th Century Dutch art at the De Young museum in San Francisco. The star attraction was Girl With Pearl Earring which was fabulous, but what kept me going back in the exhibit was The Goldfinch, the painting at the center of the movie coming out next week. We were both awed by the beauty of that work.
I could go on all afternoon.