Seeing them in person makes an enormous difference. And the Van Gogh museum is spectacular. I already liked his work, but I felt like I understood it much more, including how tactile his process was.
A particular piece that really blew my mind to see in person was Bosch's "Garden of Earthly Delights" at the Prado in Madrid. It left a lifelong impression (I've returned to see it several times). What I realized was, panning all over a high res digital version, you never get the sense of the whole or the theatrical scale of the thing. It's like watching a movie on your phone versus at an IMAX.
I had the same experience with the Garden of Earthly Delights: it leaves a lasting impression. It's so incredibly weird; parts of it look like a seventies comic (or perhaps older sci-fi book cover art) instead of a half a millennium old painting.
If I may give a recommendation :-) Another painting that left a lasting impression on me was "Virgin and Child with Canon van der Paele", located in Bruge, in Belgium. It doesn't have the weirdness of the Bosch painting, but it's just so incredibly detailed, and unlike the more famous Lamb of God, you can come to within 5cm of it.
A particular piece that really blew my mind to see in person was Bosch's "Garden of Earthly Delights" at the Prado in Madrid. It left a lifelong impression (I've returned to see it several times). What I realized was, panning all over a high res digital version, you never get the sense of the whole or the theatrical scale of the thing. It's like watching a movie on your phone versus at an IMAX.