I think FreeBASIC has potential to be better than C, simply because the syntax is cleaner and easier to learn/use. In fact, I already prefer FreeBASIC to C, and when FreeBASIC has full OOP I think I will rather prefer it to C++ also.
That said, I would never place the original BASIC over C++ or even C. BASIC has a bad name because of its bad beginning. I think the modern FreeBASIC is nice, and thus C is only more popular because before FreeBASIC the language BASIC sucked. The older BASIC sucked, and although more modern variants (QBASIC and Visual Basic, for example) are a great deal better, they still have many problems. Many of the problems C++ was designed to address still exist in those languages (although lately VB is getting better I think), and even C is better in some ways.
With FreeBASIC, we finally get to see that BASIC can be structured, procedural, even OO, and generally is capable of being a good clean decent language. In other words, we finally see that it's possible to be a serious programmer and use BASIC. But C and C++ are still more popular, for the variety of reasons mentioned earlier (more efficient, more developed with more features, and they've been serious languages for a lot longer - they have a bigger user base and more developers). Even once FreeBASIC is at that point, I suspect it will remain a niche because of the following reasons:
-More people know C/C++. The majority of programmers know and use these languages. FreeBASIC is a minority.
-More code is written in these languages. People wouldn't want to learn a new language and try to convert all their old code into it - especially if it is functionally equivalent to the other language, and doesn't really add anything new or more useful. And since most commercial programming ventures likely use existing code in those languages, people working for them will likely continue to use C/C++ too.
So what hope does FreeBASIC have? Well, I think the best hope is to help new programmers. Because of its simpler and (imho) more elegant syntax, it's easier to learn and use. So new programmers who would like to learn programming as a hobby may begin to use it, and stay with it (particularly once there are the important features - gcc emitter, OOP, etc.). Once people see FreeBASIC as a serious language, they may begin to use it. And eventually, as new companies are started and whatnot, people will be able to use it because it no longer has to compete with massive amounts of existing code written in other languages. In a new company, FreeBASIC can easily replace any other language because they have no skeletons in the closet to deal with.
I think FreeBASICs greatness is still a ways in the future, but until then, we can all help by continuing to use FreeBASIC and becoming more proficient users so we can help test for bugs and experiment with new features, and possibly eventually be able to work on the compiler. With more developers, the project can grow faster, and the more of these "dream features" are implemented the greater the compiler and language will become. As that happens, the community will grow quickly as well.