I think you guys are talking past each other. "Genocide" refers to deliberately targeting a specific group because of their ethnicity, religion, etc. The Soviet Union rarely did this - they generally targeted people on political and economic grounds. So while Stalin's regime appears to have killed tens of millions of people, "genocide" is not the proper word for it (mass murder, butchery, and so forth are quite appropriate).
The Communist leadership was quite aware that their policies were causing mass death, but John is right that this wasn't in itself the goal. They would have been satisfied with their reorganization of society even if it hadn't killed many millions of people. But they were also fine with it actually killing millions of people, which it did. Essentially the lives of those standing in the way of their political and economic plans meant nothing to them. Wealthy farmers as a class (the Kulaks) were deliberately brutalized, their food stolen from them, and so forth in actions basically guaranteed to kill everyone. And both the leadership and the Communists on the ground knew very well that their actions, such as confiscating food from starving "disloyal" peasants, were resulting in mass murder. But most of the deaths weren't an end in themselves, most of the people starved because Stalin was reorganizing farming and it was deemed acceptable if lots of people starved in the process.
A similar thing happened in China with Mao's "Great leap forward" - there were a lot of deliberate killings of individuals but the really big numbers came from starvation.
This is fairly distinct from what happened under Hitler. The typical German citizen did pretty much fine under Hitler (compared to the typical Russian who had a much larger danger of being starved, or shot/imprisoned for disloyalty, under Stalin). His goal was to exterminate specific groups as an end in itself - get rid of Jews, gypsies, homosexuals, communists, and eventually as many "slavic untermenschen" as became necessary to clear out eastern Europe for German colonization.
Another example, sort of in-between, is the Japanese. They killed a tremendous number of people in Asia. But it wasn't due to Soviet-style indifference to life (Japanese weren't the targets), nor did they attempt genocide against other populations, Nazi-style. They were more the "brutal conqueror" type - in the progress of their military operations enemy combatants and civilians were treated with extreme harshness. Their military created a culture of contempt for other societies, and special contempt for anyone who surrendered.
And yet another example of hard-to-categorise mass murder in history was the Mongol horde. At times they contemplated genocide - mass extermination of farmers to make pastureland for their horses. But their bloodiest massacres occurred following the conquest of a city whose resistance had particularly angered them for some reason, and they might exterminate the entire populace. They also caused a lot of death through Soviet-style uncaring destruction - their conquest and mismanagement destroyed extensive irrigation systems in the Middle East, leading to huge numbers of deaths from starvation and privation. The Mongols killed a tremendous number of people, but rarely due to what we'd consider genocide. Even their deliberate mass killings of civilians usually were spur-of-the-moment things focusing on the population of a single city, whose neighbors would be completely spared if they surrendered without a fight.
"Genocide" is an overused label in the modern world, and the arguments over its improper application tend to simply confuse the tremendous evil and destruction of acts which cause tremendous deaths but don't happen to target a specific group.
Let's try "belong down the list".