I really think C is much easier to get good at than other languages. There is no mystery with what's going on in the computer when you learn C, the builtin functions, how big something is, how things work, etc.
When you learn higher level languages there is significant mystery in everything. It means you can write a lot of code having no idea what's going on under the hood, which is good. That's the point of a higher level language, but it is certainly something you SHOULD know in order to call yourself an expert. These mysteries are sometimes what causes Good programmers to get hung up on odd edge cases .
Depends on the quality of the runtime. For instance, C# and Python are really good and well-documented. Your Java environment can vary quite a bit, but you probably have control over it.
Howlers like PowerBuilder and InstallShield are just hopeless amateurville and leave me giggling with awe at how fantastically bad they are; they are worth looking at if you want to get a sense of how lucky you are.
When you learn higher level languages there is significant mystery in everything. It means you can write a lot of code having no idea what's going on under the hood, which is good. That's the point of a higher level language, but it is certainly something you SHOULD know in order to call yourself an expert. These mysteries are sometimes what causes Good programmers to get hung up on odd edge cases .