As other posters have stated a stalemate in Russia is a norm in most cases, but that doesn't mean you can't break that stalemate.
When I am ready to attack Russia I typically have 6-8 Tank Groups packed into a tight group ready for a break through. Weaken the Russian line with air units, make a hole with Infanty and flood the area with tanks. This strategy is just as solid for any of the Russian lines they create to stop you.
Don't immediately attack a city, destroy the surrounding units first to maximize the number of units you can throw against a city, surround the city, reduce its entrenchment, then move in with infantry.
I think mobility is the key in most cases, encircle units, reduce their supply, readiness, and entrenchment and they stand NO chance against you.