The ones I have been to:
Antwerpen Zoo (Belgium) have a tall building with much grown vegetation inside and a very high transparent roof. They have typical asian and american species, but I saw my first Grecian Shoemaker here.
Artis Royal Zoo (Netherlands) have an excellent butterfly house with looks like a big garden, clean and neat, without letting the plants overgrown. All species here are from tropical America. Is a really very good exhibit, with also great botanical interest due to rare species of tropical trees used. Check the calabash tree trunks, they're favourite resting spots for butterflies.
Burgers Zoo (Netherlands) have the Mangrove with free-flying butterflies mixed with birds, manatees, fiddler crabs, etc. All butterflies here are Caribbean as the rest of animals in the exhibit. Most are longwings, but also morphos, cattlehearts, etc. The most interesting is to be able to see interaction between butterflies and bigger animals such as ducks or doves.
Faunia (Madrid, Spain) have the worst butterfly house I've been into. Called "the Eden garden", it only holded longwings and one Malachite during my visit. Vegetation is too dense and butterfly feeders are unaesthetic flower-shaped small red sponges attached to branches. Is always full of people and the pathway is too closed for a relaxing walk.
Franklin Park Zoo (Boston, USA) have a very good one with interesting native species mixed with some common tropical ones. In my opinion, is the best one I've been, because the native species they use are very unusual in Europe and many was new for me. In the exit they have a big Clethra bush whose flowers are always full of butterflies.
London Butterfly House (Syon Park, London, UK), I went in late 2006, and they closed forever the same year, sadly. I went here by some unusual passerines that they also kept, such as Japanese waxwing or Emerald starling.
Mariposario del Drago (Icod de los Vinos, Tenerife, Canary Islands, Spain) also closed forever since long years ago.
The conclusion is that butterfly houses alone struggle for survive, while butterfly houses that are part of a bigger zoo, can remain with no problem.