Really? What people of another religion (say, Hinduism) were able to instantly heal people of any disease or injury through prayer, with perfect results every time? Suppose you lose your legs in a car accident, but when a Hindu stands in front of you and says a brief prayer suddenly there's a flash of light and your legs have magically reappeared?
What if the followers of another religion were magically immune to any sort of harm? Bullets fired at them simply stopped in the air for no reason, they weren't affected by disease, they could stay underwater for hours without drowning, etc?
Are you really telling me that such evidence wouldn't make you ever consider the possibility that their god was real and yours wasn't?
Nope. Not even all that. Satan gives power to his followers. I am not deceived.