If you take the time to read about actual history that happened, you will notice how the games were actually played with peoples lives. Mary, for example, was very much a part of the game herself, but, unfortunately, was beheaded in the end as a result. There is an audiobook of her story here:
Here is the first half of Game of Thrones backstory that is very interesting:
Why does one story have many more viewers than the other? It’s all in marketing and style. Queen Mary was a person who lived and died under a kingdom. She conspired with people, lived through battles wars, treachery, was a part of executions, trials, feudal rivalries, trade and everything else. Her life was not a fantasy as we see how people were depicted on Game of Thrones. She had to eat, breathe and poop her own reality.
We look at the drama with Game of Thrones and can say that it isn’t real. How can people cut each other down with swords? How did all that magic happen? Why were some of these people so selfish in their ways? In the Game of Thrones, we mostly see the highlights of every day interactions that are more condensed to save time for the viewer.
The Game of Thrones map seems very similar to England:
Here is a map of England:
The land mass on the left is like England and the portion on the right may be parts of Belgium, Holland, Germany and so on. The big difference between reality and Mary is that France is excluded from the fantasy. Mary came from France and was an important kingdom to control for her. At one point they wanted to unite the France and Scotland kingdoms, which would have excluded Britain.
Britain and Scotland were constantly at war with each other. There was a border or possibly a wall that separated the 2 kingdoms. We can compare the Scottish to the Wildlings, while the British would be more likely the Southerners. The Wildlings lost their fair share of battles just like the Scottish have.
I don’t think that George Martin (author) needed to stretch his imagination too far to come up with his storyline. It just takes reading the history of the progression of kingdoms, which in many cases has been well-documented, and focus mostly on the most dramatic sequences to bring it all together. This can take a massive amount of research, but is very possible to do with the right resources. Travelling to Scotland and looking at their relics and museums can be of great help.
Here is a quote from 9Ggag that sums up George RR Martins story line: