It would seem to me that it is considerate to your wife and respectful to your son to be there. Anyone who would choose a video game over an event that will have an impact on at least two individuals they're meant to love most in the world would seem to me to be at least a somewhat alarming future father.

This is more your opinion and your own value that you're putting upon 'being there' for an event that the father likely would have no impact upon. It's entirely feasible for the mother not to care if he was present, and entirely probable that the child doesn't care. You can't just assume that since you and most mothers would want the father present, that this mother would. Thus, not attending says nothing about their character in this situation and only about how they view the importance of watching something that is out of their control anyway.