From a pure marketing perspective the problem is Master Chief is such a blank slate unless you are pretty steeped in the lore.

ie Pikachu has already sold a lunchbox by the time you have explained what the space marine guy is about.

This all seems really simple-minded but having identifiable brands are incredible business. I definitely see MS and Sony trying to Mario-ify their characters. Aloy/Horizon Zero Dawn is a good candidate for this.