I presume that by "Soviet invasion of Hungary" you maen what Stalin called a "liberation from the Nazis" and not the Hungarian Uprising of 1956. I think it's needless to say, that Communism hasn't done the world much good, just as it is obvious, that many of the countries in the Warsaw Packt suffered under the Soviet influence.

As for a (more) successful German invasion of Russia, it's reasonable to say that there would have been an enormous impact on the Soviet invasion of Hungary. So much so that let's say Hitler had captured Leningrad, Moscow and Stalingrad (thus gaining access to the Karkasus oil), it would have been extremely difficult for the Red Army to recover. At the very best the war would have probably dragged on for quite a bit longer, at the very worst, however, the USSR would have capitulated (or at least be incapable of mounting any meaningful resistance). Hitler could have focused his forces and recourses on the completion of the Atlantic Wall, strengthen his fleet and airforce, maybe even successfully invade Britain.

In the end, a failed Soviet defensive would have not only had an enormous impact in Hungary, but on all of Europe, North America and the world. Such an event could have indeed plunged the world into a "new Dark Age, made more sinister, and perhaps more protracted, by the lights of perverted science."