While Lenin was genuinely a revolutionary determined to spread Communism, Stalin was more narrowly and ruthlessly focused on personal power and the development of a commanding, centralized Russian state. HBO's 1992 production Stalin starring Robert Duvall seems the most accurate film portrayal to date. Stalin comes across as the crude leader of a gang of thugs, quite unlike the diffident, well-mannered Louis XVI or Tsar Nicholas II.
As you suggest, such differences can be disregarded so as to recognize commonalities between the Tsarist and Soviet regimes that are not unlike those between the French Bourbon monarchy and Napoleon. In both examples, there is a dedication to centralized state power, absolutist personal rule, and systematic suppression of dissent and resistance of any sort. The laws and prisons of the French monarchy and the Tsars were less brutal than those of their revolutionary successors, but they were prisons nonetheless.
Excellent film. And it's on YouTube. The scene where he visits the local Council, and orders them to seize the grain from the peasants is the most chilling.
Another movie that just came out is called “Dear Comrades” about the massacre at a factory in 1962 after the workers went on strike.