I had a similar experience with Rothko, though not as strongly as you and lissener. But it was definitly the “lightbulb” effect. One look at his work in the flesh, and something that I’d never seen the appeal of just clicked for me. Not just him, but minimalism in general. Color has always been one of the tools artists have used to convey emotion, but Rothko could do more using only that tool as most other artists could do with a fully equipped metaphorical machine shop. Rothko was a fucking samurai. He opened up a whole bunch of other artists for me, too, who did the same thing using other tools.
My real Road to Damascus moment was when I saw Guernica in person. I’d seen reprints of it over and over, and while I didn’t dislike it or anything, I thought I’d “gotten” it. Then I saw it in Madrid, life sized, and I almost ran from the gallery. It was overwhelming. It made me sick to my stomach. It was amazing. I’ve never been so affected by any other painting. Hell, there are damned few works of art in any medium that have affected me like that.
You remember a few years back, there was that guy who had stolen billions of dollars worth of art over the years, and his mother dumped most of it into a canal so that it couldn’t be used as evidence against her son? I remember arguing here that it wasn’t really that big a deal, because we had photographs of most of it in art books and the like.
I was a goddamned idiot.