The Halo series has reinvented first-person shooters. Even though Halo: Combat Evolved was only released in 2003, it is considered a classic. It has a really good story, and great graphics and sound. However, there are some serious problems. Sometimes, when enemies drop their guns, they'll get stuck inside environmental objects, spin around slowly and emit a horrible grinding noise that can be heard quite a distance away. Plus, Master Chief (the protagonist) scarcely talks. I'm halfway through the game and he's said about 120 words.
Despite being rated M, halo isn't that inappropriate. The blood is ULTRA unrealistic, even that of humans. The thing that parents should be worried about is The Flood, a parasitic life form. The Flood starts out as cat-sized insect-shaped blobs, and when it infects someone, the effects are pretty gruesome. When The Flood infects a type of enemy called an Elite, the Elite's skin turns pale greenish brown. It's left hand is replaced by a whip-like cluster of red veins which it uses as a secondary weapon. The Elite's neck is lengthened and it's head is curled backwards, and another whiplike cluster of veins sprouts out of the chest. The really gruesome thing is, when you shoot them, it spurts out dark green blood and, if you place your shots correctly, you can shoot it's limbs off, and I've seen tiny chunks of flesh fall off, too.
There isn't much sexual content in the game, but the holographic representation of the A.I. Cortana can get to be a little much. She's completely naked except for black lines covering up her bad parts.
The only people who ever swear in the game are the Marines, and they only say mild words. However, Sgt. Avery Johnson described the space station/superweapon Halo as "God's own anti-son-of-a-b**** machine".
One more comment is that CSM got the platforms wrong. It's available for windows, PC, Xbox and Xbox 360.