The question is, if Greece managed to leave euro, that could mean other countries which are also in debt can also follow suit and do the same. Eventually when more countries follow the same action, it can only mean that the whole union will collapse. These has been projected to happen for some time now and I see no other solution.
Maybe, in the end, that's the best solution: a collapse of the whole union. Although it's hard to say, but I think many (wealthy) countries in the EU think they should never went for the Union in the first place. Many people here in the Netherlands argue that we should have kept the Gulden instead of going for the Euro. This has huge advantages, but sure, it also has disadvantages.. I don't know what would have been the best.