I've been playing this game for about a year now, it i've got to say it's really good.
The story is a complex one (bonus points from me), it's about a man by the name of Jim Raynor, who used to work with the current dictator of the government, Arcturus Mengsk, to overthrow the previous government. But Mengsk betrayed Raynor and left Sarah Kerrigan, Raynor's love, on a zerg infested planet to die. (there is a cutscene of this, but it cuts off right when the zerg are circling her. The zerg may be scary for younger kids.) Now Raynor fights against Mengsk, who has turned into a high up dictator who anyone would want to be brought down. But the loss of Kerrigan destroyed Raynor, and all he has left is revenge on Mengsk. So as he fights for a honorable cause, it fights it for a dishonorable reason.
Then it turns out that the thought destroyed zerg have returned, and at their head is Sarah Kerrigan herself, only a twisted version of her. And now Raynor fights both the dominion and the zerg, all the while trying to figure out how to save Kerrigan.
So basically there is no good role model, except for Raynor's second in command, who actually fights the fight for good reason. You do begin to connect with Raynor later on as he begins to redeem himself, but at first I questioned wether i wanted him to win. There are other characters, both funny and dark, but they don't get a lot of screen time.
Just so you know, there is swearing (never goes to the f word, thank God), there is drinking and smoking, and of course, violence.
I have a bit of an issue with the violence, but it's fixable. Simply go into settings, set the graphics to medium or low, and uncheck the 'Violent deaths' in the parental controls box. Don't go to ultra graphics if blood and gore bothers you, even with the unchecked box the deaths are still pretty gruesome. If you don't you'll be dealing with blood and flying body parts as the units fight it out. The worst are the zerg deaths, even the buildings are made out of organic material, so they explode as such. And the big zerg are even worse, so please, if you have a young kid, follow my instructions above. I'd also like to warn you that the game has its own version of 'zombies', seeing as the zerg can 'infest' people to fight for them. There is an entire mission devoted to that topic, but it's optional at least.
As for the gameplay itself, it is awesome! The campaign is ridiculously fun, with many different varieties of missions to do, from trying to reach a target mineral amount as you fight zerg at the same time, to escorting civilians to a ship to escape a planet. Sometimes you have to retrieve an artifact by infiltrating an enemy base, others you have to wage a full out war. The ai knows what it's doing, so you have to think about staying alive and attacking at the same time. The game gives you every unit you would ever need, from marines for the front line to massive battleships for a heavy airstrike on an enemy base.
But the real game is in the multiplayer. Play solo against another solo, or team up to an amount of 4 players per team. There is even a free-for-all mode! The Battlenet matchmaking system pits you against players of your skill, so you are constantly challenged.
But be warned. This game is NOT easy to learn. Even if you did awesome in the campaign, the multiplayer is a whole other game. Things get high tec, FAST. It's common to have your mineral supply sniped by some void rays in the first 10 minutes of the game. And then there are the pro players. Thankfully the matchmaking system prevents you from having to play these people, but they use the keyboard in everything they do, sending their APM (actions per minute) into the hundreds, thousands even. If you want to excel at this game, you need to learn each unit, how to counter them and when to use them, learn the different strategies for the different races, how to expand your mineral supply quickly, when to strike and when to wait, so on and so forth.
Or, if you aren't into that kind of thing, check out the arcade. This section of the game is one where players of the game, took it, modded it, and turned it into something else. For example, there's a game called Squadron tower defense, where you build units to prevent the creeps from destroying your security system. Or there's Empires and conquest, where you conquer other empires by destroying their command center, and they then fight for you. The list goes on and on, even including a game called proton cycles, where you fight it out, Tron style, riding cycles that leave trails of deadly light behind. The games are endless.
So my final verdict is: this isn't good for kids under 14, (unless your kids are like me, kids who were exposed to the dark side of the world, and taught that it was bad and why) but otherwise i would recommend it. It's well built, the story is good, the gameplay is phenomenal, and you can play the arcade if you don't like the multiplayer.