van Gogh Museum
The van Gogh Museum in Amsterdam houses the largest collection of van Gogh's work in the world. In 2013 it had 1.4 million visitors. It's busy, but because tickets are set to a particular entrance time on a specific day, the crowd control works to keep it from being too busy. This has two downsides: 1. If you use the IAmsterdam City Card to get in, you have to line up outside before they open to get in. 2. There's no photography allowed since it slows down the viewing.
The lack of photography was really a drag for me, because I wanted lots of closeups of his magnificent brushwork. You can see I actually got a couple before the guard (very politely) shut me down. That said, however, it's a life-altering collection of van Goghs. And, we were especially lucky because there was a special show comparing the work of van Gogh and Edvard Munch (the Scream). That was too wonderful for words! Truly, a breathtaking experience.