But perhaps you wouldn't if it were a common occurrence that the villain loses.

Stories in general will almost always have the villain lose in some fashion, and the reader/viewer/player/etc. expects this. Even though the reader is sure the protagonist will pull out in the end, they know that in the end they will almost always win.

Playing off of that expectation also makes things interesting, like in the Princess Bride when Prince Humperdink and turns the Dial on the The Machine to 20. Even William Goldman steps in and tells you what happens, and because it goes against what should happen, it helps to keep the story interesting.

So if it were common that the villain won, would you root for the protagonist? No way to know, but it's interesting to think about.