Content is obviously very important, but I think another strong factor would be location. This covers a lot of aspects that can either seriously detract or notably enhance the experience of the exhibit. Not only where the exhibit is showing geographically, but how that location chooses to exhibit art and when.
The environment in which art is experienced has a direct impact on the perception of the pieces, so I think it would help with the success of the show if there was a conscious effort on the part of the artist (or their publicist/promoter/etc) to choose locations that positively impact that method of delivery.