After playing this game, you will really resent the developers for ruining the great RTS franchise.
Graphics/Physics:
It is year 2008 yet the graphics of Red Alert 3 still looks like a slightly improved version of Command & Conquer: Generals. It shouldn't be a huge problem if you are not specific about graphics, but you will have bigger issues to deal with. The outrageous, bouncy physics may seem funny at times, but this also shouldn't be that big of a pain. Red Alert 3 isn't a good-looking game, but it isn't an ugly one either. I suppose its looks will become satisfactory after having a few drinks.
Gameplay/Plot:
Granted that the Red Alert franchise doesn't pride itself for having overpowering plotlines, Red Alert 3's plot really borders on laughable. It seems that the writers deliberately accentuated the rampant cheesiness from the previous two releases in this one.
The story arc is built on a "what would have been" scenario, when Japan becomes the third superpower in the world along with the Allies and the Soviets because the atomic bombs were never dropped on Hiroshima and Nagasaki. This clichéd alternate universe setting is just a cheap excuse to shove in a new faction into the game. This can be forgiven if the campaign story turns out to be outstanding. Alas, it isn't.
The campaigns are divided into three lines about three distinct factions in the game. The stories in each factions' campaign are independent of each other, so what happens in the Allied campaign will not affect what happens in the Soviet campaign. The introductory cut scenes are painful to watch. Before each battle, large-breasted secretaries, who can never be taken seriously because their cleavages are just way too exposed, brief you. Along side them are familiar Hollywood actors who will dedicate the worst performance in their career to this game. If you are asking for a deep, complex story, you are barking at the wrong tree here.
The Allied and Soviet units are inherited from Red Alert 3's predecessor Red Alert 2, with several new ones that really don't make that big of a difference in battle. The Empire of the Rising Sun (ERS) units are very unoriginal and boring, generally designed along the stereotype that Japanese has cool and neat technologies. In general, the game is quite well balanced, and the developers did a good job in varying the playing style for each of the three factions.
Perhaps the most annoying aspect about Red Alert 3's gameplay is the retarded control system. You will frequently find your units not taking the shortest route to their designated destination (with no obstacles on the way) and take a very long detour. This can get incredibly frustrating at critical moments. A good RTS game just shouldn't have this kind of problem.
A new feature in the game is the co-commander system, which is just an ally who you can give instructions to. This is again not an original idea because Age of Empires II already executed a very similar concept. That's right, Age of Empires II.
Multiplayer:
Although Red Alert 3 is hardly a classic, it does a good job in balancing units and varying playing style in each of the faction. Therefore, the Multiplayer experience shouldn't be all that bad.
Fun way to play:
Make sure that when you are playing campaign or single player skirmish, at least set the difficulty to be normal, because easy enemies are just WAY too easy. To illustrate this, I once got incredibly intoxicated (bad, bad hang over the next day) and set myself against two camps on the same team (both on easy), and I still could beat them singlehandedly.
Conclusion:
Red Alert is a good franchise, but the terrible production rendered Red Alert 3 into a poor, pathetic game. It seriously isn't worth your money. If you really want to try it out (and be dissatisfied), just rent it.