What is the best pokeball to use against virizion in Pokemon white version 2?

Because this is a legendary, I wouldn't recommend using a quick ball, however ultra balls will work just fine. Virizion isn't very hard to catch, so don't use a master ball. If it really is taking you more than 30 so turns to catch, either restart or start spamming timer balls, which will start to be effective at around 10 turns. Try to bring it's HP to 1, with moves such as false swipe, though watch out because when it runs out of PP it will start to damage itself with struggle. Once it's done that you might as well restart.