Halo 4 is absolutely amazing. I don't think it's as good as Skyrim, but I still love it. Thought Halo 3 and Reach were good? This is ten times better than them. The graphics are splendid, almost like you're watching real people, and the story is fast-paced and exciting. New vehicles, enemies, and features have been introduced to Halo 4. A problem is that the game is a bit too hard, and some levels should only be played co-op because of their difficulty. However, there is an "Easy" mode, for the novices. I think Halo, as a shooter, is somewhat better than Call of Duty in originality and introduction of new features. One minor complaint, is that some of the multiplayer Custom Games have been removed, and the existing ones are harder to find on the interface. Now, onto the appropriateness level:
VIOLENCE: Moderate. During most of the game, you will be pitted against aliens known as the Covenant, and a new robot-like race called the Forerunners. As you can tell, there is plenty of violence in this game, but none of it is especially graphic. Shooting an enemy results in a small spray of blue, purple or orange blood, which can splatter on nearby surfaces. There is no sign of dismemberment or injury detail and the violence is justified as you are fighting against evil aliens. Humans can be killed, but you generally receive penalties for doing this. Also, you can perform "executions" during melee combat, where you finish the enemy off with a third-person blow such as a curbstomp or neck-break. Trust me, this is not as bad as it sounds, and shows no blood whatsoever. This website decided to give this game a "Not For Kids" rating based on just that. And then they give The Walking Dead a 16+ rating. Executions were also seen in Halo: Reach, but slightly less frequent. Common Sense Media, you've really gone crazy with your ratings this time.
SEXUAL CONTENT: Very mild. There is a character called Cortana who is an AI (artificial intelligence), who has a somewhat revealing costume, with only wires covering her sensitive areas. She is featured prominently during the game.
LANGUAGE: Mild. Occasionally, words like "d**n" and "h**l" are used. I also think I heard "b****rd" and "b***h" during the game (there are some crackly radio transmissions where it is unclear what the characters are saying). The language is nothing you wouldn't hear in a PG movie though.
SUBSTANCE USE: None. There is no use of substances in the game that I remember. If there was any in the game, it definitely wasn't anything debatable for a kid to see.
OTHER: Towards the end of the game, there is a frightening scene where a group of people melt. It is more shocking than graphic, and definitely shows less than a similar scene in the first Indiana Jones movie. I didn't really want to put this in the "violence" section because it wasn't, really.
Overall, this is a great game that encourages teamwork, and good versus evil, and has little concerns. I would say that the youngest age to play this game should be 9.