In a personal view point, i think that you need to know C/C++ is a good base to begin in videogames development, because there are other languages as java or c# with a sintax like C and that can help you to learn it quicly.
A professional game programmer who does not know C++ is probably at a disadvantage. Beginning game development in either C or C++ is in my experience a very bad idea. Neither language is in any way forgiving to a beginner in programming, especially because things easily 'appear to work' but are in fact horribly broken.
Saying languages like C# and Java can help you learn C++ or C quickly is simply an obscenity. First, you learn languages on their own terms. Knowing other languages certainly makes it easier up to a point but the biggest task in learning any language is learning it idiomatically. If a skilled C programmer writes C++ code largely like they write C code that usually ends in a 'worst of both worlds'-state. That is despite the fact that C++ and C share a very close relationship (some of the first C++ compilers even generated C code to do the actual compilation).
This does not get any better when looking at Java and C#. Some of the worst C++ code I have seen in my time was made by people who had some Java experience but were absolutely clueless about idiomatic C++. C# programmers are probably guilty of similar crimes but there were never that many around the code bases I have to deal with.
The other core complaint here is using 'quickly' in the context of 'learning C++'. C++ is not a language you learn quickly. And I'm saying that while loving the language (despite or because of all its rough edges).