There's a reason people evolved altruistic reactions and tendencies, and that's because on some level, altruism and trust in a community is good. How could anyone trust anyone else in a society where backstabbing is essentially the norm? Building giant projects like power plants could not exist without humongous inefficiencies if everyone were to constantly be trying to insure themselves from everyone else's manipulation and making sure that they have a slice of the power pie and are not beholden to anyone else. If a society of Good people are all able to trust each other beyond any doubt (because Good people are inherently trustable), they can actually do insanely long-term plans knowing that those following them will continue to meet their obligations. Resources will be split more evenly ensuring maximisation and therefore a larger force.

Your example is also incredibly simplistic because nobody wins in a nuclear scenario, and that's why Good would be opposed to it. It doesn't mean they're against other means of stopping the issue that don't contravene international laws (which, by the way, would be 100% made by Good people because Evil people would have no reason to be a party to any of these treaties).

If nuclear war happens, everyone loses.

With conventional war, it's a wash, but I'd give it to Good, with one side having harsher tactics (but also a chance of internal conflicts and opportunistic coups) while the other side has more resources but may only fight defensive wars.

With no war, Good wins - seems like a win for Good to me overall. The only problem is in real life it's much harder to separate the Good from the Evil, and most people (myself included, probably) are somewhere in between.