I love Hungarians. Polish and Hungarian people have really old, brotherly and loyal relations with one another (http://en.wikipedia.org/wiki/Pole_and_Hungarian_cousins_be) like almost no other nations in Europe.
But, I don't support Hungary going back to Kingdom borders simply because it is impossible. What is meant to happen with all those Ukrainians, Romanians, Serbs and Slovaks? Many Hungarians say they don't care where they go as long as those lands go back to Hungary, and frankly, this is just stupid and offensive. Hungary does not have military power to take on Ukraine, Romania, Serbia and Slovakia in war to get their historic lands back anyway. Best thing is to just ignore such people.
It would be like me claiming Polish-Lithuanian Commonwealth borders as what Poland should be. : Yeah, right.
I would perhaps suggest Hungary going back to its Horthy-era WWII borders, since this would be demographically correct. There are still many Hungarians in Transylvania who deserve to be linked to their homeland country, since this is their land too.
Though on other hand, I know how Hungarians feel. Poles lost much land after WWII as well, thanks to Stalin. Many old Polish towns and cities are now in Ukraine, Belarus and Lithuania. But, unlike Hungarians, I do not seek this lands back, or anything. What is done is done and I would never agree to some stupid war again in Europe over land just to get some old lands back where there are hardly any Poles living anyway. Now, there are Ruthenians/Lithuanians (many of whom were already living in this cities anyway in ancient times) with lives, jobs, families, friends and homes. I would NEVER, if I had position of power, want to destroy this lives just to get some old land back. Poland has enough to deal with without taking new and unecessary tasks.
Same as situation between Poles and Germans. I would perhaps agree to Germans getting East Prussia back, maybe even Pommerania and Silesia, as long as we would get Eastern territories back and Ruthenians (Ukraine and Belarus) could get oblasts in Russia that historically belong to people of ancient Kievan Rus and which still have Ukrainian and Belarussian majorities).
But this is all just talk anyway. Nobody seems to think or care about implications of "giving lands back". Millions of peoples' lives would destroyed. Homes lost, jobs lost, neighbourhoods (friends/family) torn apart, and what happens to this people when they arrive to some part of land "given back to them", people who have children to feed, special circumstances, or whatever. Not to mention relations between nations, since most peoples living there now have nothing to do with why those borders were redrawn in first place.
Historically, we have seen effects of such expulsions and border-reddrawings. Over 1-million Germans died during deportations from all parts of Central and East Europe, several hundreds of thousands died after being kicked out of their lands in former East territories and thousands of Ukrainians died in Akcja Wisła, not even to mention tens of millions of displaced Germans and their families families, millions of displaced Poles and hundreds of thousands of displaced Ukrainians. Just for fucking land.
Never again. No to Greater anything.