Good Question CoolDude!
Unfortunately, to my regret 90% of the people who replied are promoting sectarian views by claiming that they * are * right.
But the sheer reality is that we with our imperfect wisdom have a great probability of being wrong.
All Muslims among us pray, and in their prayer they recite the Surah al Fatiha which has a verse as follows:
'ehde naserat al Mustaqeem, serat al lazeena an amta alaihim, gair il magdhoobe alaihim wala-dhaaleen'
We are basically praying to God:
'Show us the Straight way, The way of those on whom you have bestowed your blessings, those whose portion is not wrath, and those who go not astray'
The prophet prayed this, all the Sahabas prayed this and to this day all Muslims pray this. This basically proves the fact that no one is perfect, and one who is right today in one matter, maybe wrong tommorow in the other.
So we have to consequently seek Allah's guidance, and not be ignorant towards other beliefs for our own sake. However as Alpha1 put it we should be subjective and judge using the great Criterion we have been given by the Most Gracious...the Quran!
WS,