One of the main reasons why many companies use C++ is because when the language was in early publication versions it was actually quite useful and gained a lot of attention. Those massive numbers of students eventually got deep into the industry, so we are seeing the maturing of that C++ subculture. That same maturing of both the language and the students into careers happened to Java and is going to happen to C# (already is to a large extent).
The C++ and supporting libraries, like several major languages, are very powerful and will be used for years to come.
Keep in mind that every language has strong points and other weaker aspects which may be better satisfied in another language, which is why we actually see several other languages commonly used alongside C++ in the game development industry. For example, C++ is very favored for multi-threading and managed memory coding of areas of the game which are fairly constant, such as handling object loading, terrain issues like cloud to mountain clip hint to be more specific. In areas of the game which stop and start as the player makes decisions ingame, then an auto-memory management language implementation is often best, such as using Lua for scripting events by "triggers" as the main character does the role play thru the game scene. Another way of looking at it is when smooth implementation and render to screen is critical, then C++ shines bright with things like weather and terrain, but it may be much faster game development to use another language such as Lua, Python, Java, or C# for areas of the game where smooth rendering of the object on screen or other gameplay feature can afford to have a slight delay, such as a group of zombies suddenly rounding the corners of buildings when the character reaches a certain location. (Don't misunderstand, because all of these languages may be coded for very fast performance, but many people find Lua, Python, Java, or C# much faster to develop when used for not-performance-critical areas where these languages are typically quicker in development from start to beta.)
Clinton