You may have gathered from reading other various pages on the site that I am a RTS fanatic. I love Command and Conquer. I have spent a large chunk of my life playing the C&C series. This was the game that started the whole RTS explosion, forget all those imitators like Age of Empires or Starcraft. It's all about C&C. The story follows the Global Defense Inititive (GDI) as they battle a worldwide terrorist group called The Brotherhood of NOD which is lead by the enigmatic Kane. Behind it all an alien substance called Tiberium is slowly spreading over the entire world.
The basic control scheme is taken from Dune II and expanded upon. Now you're able to draw a window around multiple untis to control many at once. You're also able to assign a group of units to a team number. Controls are simple and easy to get the hang of, the game itself is like a high speed version of chess. Units use the paper/rock/scissors method of strengths and weaknesses (as in one unit type is vulnreble to one type of attack while another is immune, and so on.) Playing the computer is fun and the missions are interesting, but the real fun comes in matching against a human opponent. Where the C&C series excells while others fail is that C&C doesn't require you to micromanage anything past base power and money, everything else is taken care of (you don't have to feed your units like in say Warcraft, nor have fuel for your vehicles, etc.) This effectively allows you to concentrate on what matters most: Stomping the crap out of your enemy.
The possible combinations and strategies that come from building your own personal army is almost limitless. Build your base wrong and you may be vulreble to a certain type of attack but protected from others, build too many of one unit and you might shortsight yourself if your opponent builds to compensate. GDI has the overall advantage with better armored units, while NOD goes more for stealth. Unit types are pretty basic, gernaders, flamthrower troops, minigunners, humvees, tanks, artillery, etc. They start getting interesting later on in the game, when weird specialized units start showing up, like Flame tanks, rocket bikes, Stealth tanks (which can disappear to sneak past base defenses,) and the Mammoth tank, which is the big bad ass of the game.
The original C&C hasn't aged very well, graphics look pretty dated (and small.) The SVG graphics in this version are more detailed than the DOS version, and actually let you see a lot more of the map on screen. Some people may be turned off though at the lack of detail or the obvious bluescreen used in the CGI cinema scenes. Getting it to run under Windows XP is also a major pain but possible with a patch.
As this was the first C&C a lot of things can be forgiven, like the lack of veteran units or things like radar jammers. Some RTS conventions that are taken for granted today had not yet been developed in this game, such as the ability to cue units when building them or teams showing what key they're assigned to. However the game itself is still a milestone. The two sides each have their own look, strengths, weaknesses, and competing world philosophies. GDI Vs. NOD, kind of like G.I. Joe. And unlike the other C&C games, the acting in this one is not so embarassing. The plethora of mods all over the internet for this game continues to breathe new life into it over 10 years after it's release (I've even found one that lets you build the Millennium Falcon, armed with the GDI Ion cannon.)
And of course, Kane is the man.