Mine is Hermitage (Saint Petersburg). It has the most items 3 million but the visitors can see only 600.000 of them. It is also very luxurious and has a vast collection from greek and egyptian art, to paintings and the treasure of the tsars. It is certainly much better than Louvre which is in my second place. Third will be the Acropolis museum. It really impressed me especially as a structure and it is nice to see the ongoing excevation from the glass floor.