>>9
C++ is akin to Windows or to the English language as a standard. There's nothing amazing or incredible about it, except possibly backwards-compatibility and being easy to pick up if you already knew the previous mainstays (C and Pascal), and it became dominant more due to historical circumstance than anything else. It's true that everyone should know it, but that's because you're probably not going to get a job in programming without it (or with Java, which is closely related) - and you may want to want to interface with a C++ library in a language for which no bindings exist at some point, so it comes in handy to know it then.

Lisp and similar languages are talked about here because they use different paradigms from most 'popular' languages and are a great way to open your mind, think about problems in different ways, and increase your productivity. Even if you're in a situation where using something other than C++ is impractical, being well versed in languages that are very different will have made you a better programmer.

Ideally, you should dabble in as many languages as you can (within reason- you'll find that some of them have nothing new to offer over others except syntax tweaks or garbage collection, while others will introduce you to a totally new way of thinking; focus on the latter) to increase your problem-solving skill. If you particularly like one, it's fine to delve deeper into it, but keep your mind open and don't fall into the trap of believing C++ is the one true language or Scheme is the gospel of programming. Every language has its uses and benefits, depending on the situation.