Command & Conquer: Red Alert asks one question: what would happen if Hitler never existed? As a sort of side project/pseudo-sequel to the original Command & Conquer, Red Alert begins with Soviet scientists going back in time to assassinate the uber-fascist. The consequences are felt throughout the series but in the original, war breaks out anyway, and you can either side with the Allies (who are admittedly a little dull) or with the Soviets and Stalin himself.
As early RTS games fare, C & C was popular because of the asymmetric faction design. One army would specialise in fast, lightly armoured units, while the other built heavily armoured units with greater firepower but which were significantly slower. Red Alert carried on this trend of asymmetry, with Soviets gaining access to Tesla Coils, the Mammoth Tank, and other unusual technology, while the Allies specialised in more conventional vehicles and the Longbow Helicopter.
But the thing I loved were the FMV cutscenes. The live actors brought a B-movie quality to things, which only got better as the series progressed, culminating in possibly the greatest Tim Curry performance ever. It made playing as the Soviets fun, with their awful Russian accents and (more) eccentric take on Stalin. It's not just the cutscenes that got in on the B-movie theme. There is an entire campaign where the allies must defend civilisation against a horde of giant ants. It's as ridiculous as it sounds.
With a remastered version of Red Alert being worked on, which will include all three of the classic expansion packs, you'll have a chance to play soon (or you can play a free version called OpenRA). It's unclear if the original cutscenes survived for the remaster, but I sincerely hope they did. We should at the very least get 4K ants.