In the event of the scales tipping towards defeat of any side with nuclear capabilities, I believe the swarm of nukes would be very hard to stop, causing all out destruction and more importantly, the fallout that ensues. It's therefore most likely that a winner would be a nation far from those involved, that would emerge as the 'winner', purely because they'd be the only ones left to take the 'spoils' of highly irradiated land mass.
Anyone who says that there is not a real winner in war is very mistaken. As in tradition, the victor of any war takes the spoils of the war. Whoever gets the spoils is the victor! In World War 1, the victors got compensation and territory. In World War 2, the victors carved up Europe. In World War 3, the victors will win something similar.
There are many other examples. In the US's "splendid little war" with Spain, we won territory. The same going earlier to our war with Mexico. Perhaps the only example of a draw would be the War of 1812.
World War 3 would most likely start like World War 2. Evantually one country would be invaded then another attacked dragging everyone into war. The only problem is that so many nations have access to nuclear weapons that it would end up being a nuclear world. This could possibly lead to the end of the world due to nuclear fallout and the sheer amount of destruction. So no one's a winner.
If a World War 3 happened, there would not be a winner. In every war even if someone can declare victory, the true outcome of the casualties would be devastating to anyone. I believe Wars cause nothing but undo stress on the economy both financially and emotionally. There would be nothing good to come out of another World War.
War has no winners. If world war 3 happens it will be catastrophic. Because there will be no loser and the world will end by nukes and weapons that also affect ecology so basically you are committing suicide. Now countries that would spark a world war 3 at this moment would be North Korea, Iran, or Syria.
No one wins in war. The casualties would be well over 2.3 million. I'm no scientist but I'm pretty sure World War 3 would be apocalyptic. I think they thought that about World War one, and two. Todays weapons are most likely beyond my comprehension. Nature would end up like Chernobyl or something.
With the current level of international weaponry (both conventional and others) , if even a small portion were to be operationalized it would create catastrophic consequences even for non-combatants in the field. There would be no spoils for the victors if that is what you imply. This would be a lose - lose situation for the protagonists and the antagonists.