My alternate-history forum has produced another interesting road not traveled. It's called "The Imperious Chairman" and diverges from our history when Yacov Sverdlov, one of the early leaders of the Bolshevik movement, survives rather than dying in 1919. The author (whose handle is Napoleon IV) goes with the idea that the official story of his death--he got the Spanish flu coming back from a trip to Kharkiv--was accurate. He doesn't go to Kharkiv, and so he survives.
The main thrust of the timeline is that someone other than Stalin becomes leader of the USSR. I find the notion that Stalin's horrors were necessary to defeat Hitler rather aggravating--the book Bloodlands shows Hitler actually used the horror stories coming out of Stalin's USSR as fuel for his demagoguery and I posted a friend's essay on Bukharin (part one here, part two here) to show another realistic path--and Napoleon IV gives this leader a chance to prove his mettle against the Great Evil One.
*With a surviving Sverdlov, the internal factional politics of the Bolsheviks are rather different. I did take a class on Modern Russia at the University of Georgia, but I don't remember if we ever got into that much detail.
*Sverdlov's survival in turn causes some other earlier Soviet leaders to die--not due to anything he does specifically (like warning them about an assassination plot or inviting them all to dinner some night so they avoid a doomed plane), but due to the butterfly effect (changes spawning more changes). This makes the period between Lenin's death and what would have been the rise of Stalin more complicated.
*The Soviet Union pursues a more aggressive foreign policy during the interwar period. Although the isolationism of "socialism in one country" is greatly exaggerated--in We Know Now, historian John Lewis Gaddis describes it as something more akin to Russian imperialism than something truly international--someone other than the very cautious Stalin at the helm could done some serious meddling. This will have its consequences, both in the short-term (the lead-up to WWII) and presumably in the long term.
*Hitler still comes to power in Germany, albeit rather differently than in our history.
*With no Stalin we have no purges, meaning the Soviet military isn't the "stumbling colossus" that the Nazis spent the first years of the Eastern Front kicking around. There's still collectivization, although it's done in a more competent and less insane fashion. Many, many people still die, but no Holodomor. Not only does the USSR have millions more soldiers to fight the Nazis, but there won't be so much hatred for the regime for the Nazis to gather allies with.
*There's no cult of personality comparable to Stalin's--the alternative leader seems to view the adulation he gets as kind of a joke.