Just because the majority think something, doesn't mean that they are always correct.
Take religion for example. Logically speaking there has to be only one truth (even if there is no proof as to what that is and we have no idea what religion is true, if any). Yet, if Islam were determined to be the one true religion (I'm not saying that it is), that would mean everyone else who does not believe in the Islam religion is wrong. This would include Christians, atheists and agnostics. Therefore the majority of people worldwide would be wrong.
Of course there are other examples that could be used as well, such as the widely held belief in ancient history that the Earth was flat. That was an opinion and belief held by many people in ancient times that we have now proven to be wrong - we know for a fact the Earth is round.
The opinion of the majority of people is just that - an opinion. That does not mean it is the truth any more than it means it is not the truth. It is merely the opinion of someone, a passing judgement that the larger group of people happen to agree with.
So in answer to your question, no the majority's opinion is not always correct.