I like both of them and for different reasons. GoT takes us to different royal houses whose characters have unique and peculiar qualities; The negative characters sometimes can be remarkably ruthless and sometimes extremely untrustworthy but all of them have a kinder side also (like the Hound or Jamies). The murder of the kind and worthy like the Starks may hurt the fans enormously but may be its a part of how the entire story line has been composed.
The Starks are being butchered violently, however the Lannisters are facing the same fate, rather slowly and with much more fatal consequences, losing all their heirs unlike the Starks where there still are John Snow, the two little brothers lost in the woods and off course Arya who have every opportunity to surprise us in future. In short, it has everything to charm every sort of audience, having apart from princes and knights, Sorcerers, evil spirits, Ghost walkers, Giants (Mostly inspired by Irish folklore I guess), Dragons, gladiators, secret assassins, wolves and what not.
The Vikings on the other hand more about the aspirations of a single man, Ragner who epitomizes the 11th century Viking expeditions of Britain and their subsequent amalgamation into the society and Christianity. Vikings is more close to historical realities (even the names of English monarchs are strangely the same), keeping Ragner in the center. I have not watched their third season yet, but can expect it equally thrilling as their two previous seasons had been.
