The Allies tend to rely more on combined arms, meaning their units have to work together in order to be successful. Being a lifelong Generals player, I find the Soviets to be more fun because they get heavier tanks and their strategy revolves more around brute force, which makes them similar to the Chinese team from Generals.
The player is then given the choice to fight for either the Soviet Union or The Allies. America tries to respond by launching nukes, but Yuri is able to mind control the personnel responsible for the missile doors and lets them explode in their silos. The Soviets initiate the third world war by launching a surprise invasion of the US, with huge, bomb-laden blimps called Kirovs leading the way.
Following the Soviet Union's defeat in the first game, they install a new leader, Alexander Romanov, who plans to invade America with the help of his psychic assistant, Yuri. The game still takes place in the alternate reality where Hitler is killed by Albert Einstein, thereby eliminating the second world war. Red Alert 2's plot is set after the events of the first Red Alert, in which the USSR tries to invade Europe in the 1950s but is beat back by an alliance of different countries called The Allies. Even so, the storyline of the game itself does mirror the real life cold war in many respects. If you go into it expecting realism, you're going to be disappointed. This gives the game a fictitious feel to it, as it's not meant to be taken all that seriously. The acting in them is cheesy and over the top most of the time, and you can tell the actors enjoyed what they were doing. Not to mention, Generals does not feature the full motion cutscenes this game is so well known for. Most people think that the games that preceded it were much better, as they had more interesting storylines and more creative units. While Generals may be my favorite game of all time, I am in the minority when I say I like it the best out of all the Command and Conquer games.