Why does noone like Samurai?
Samurai would kick a pirates arse. They'd probably do the same with a ninja, and if anyone was to stand a chance against a Viking, it'd so be a Samurai.
These are men who have devoted their lives to the way of the sword, the art of killing. I'll admit, an army of Samurai against an army of Vikings, Vikings would probably be the victors. Samurai would do much better than Ninja's or Pirates though.
I'll bet on my Musashi against your Thor anyday.