Second that!

why dont they rewrite the java VM in assembley it would be faster. maybe its too big.

because there's no need to. It's plenty fast enough as it is, and the way it's coded now a lot of the codebase is platform independent (meaning it compiles equally well for all platforms Sun supports), reducing lead time and investment drastically.
If written in assembly (or worse, Visual Basic) they'd have to rewrite the entire thing for each hardware and operating system platform supported, which by now has reached quite a number (Sun supporting both 32 and 64 bit versions of Windows, Solaris, and Linux, for a total of something like 10 different distributions).

Yeah, I first noticed that "java" executable is written in C/C++ when I had some hotspot error and it wrote down a core file, whose pstack showed calls from main()->createVM()... So it's C at least if not C++.
You can execute "file java" on unix to see this. Also if you have some tools to list out names in a file like nm, or c++filt...

Anyway, that is no scale to say that C/C++ is better than Java.

For the original question, I would say that decide the industry (telecome, services, product-based, web-services...) you wanna go to, and pick based on that. If you donno which industry then just leave C/C++ and Core Java all 3 of them, shouldn't take you long to learn the languages. It will surely take some time to actually be good at programming in ANY 3 of them. Coz write code and write good are different things.
Abt java, given that apart from core java you have a 100 other things you can learn e.g. J2EE itself is a Pandora's box.

A personal note: every time I have interviewed a candidate for a job in my projects, I have looked for language/theoretical knowledge and good attitude in freshers (just outa collage) and programming knowledge in candidates with prior experience.

JRE is platform specific. You can't ftp /usr/bin/java from *nix to a windows machine and expect to run a java program using that.
By not writing it in assembly they don't save on that front. I presume, it's just that it's easier to do it in C/C++ than in asm.

I know that full well. The BINARIES are platform specific.
A lot of the SOURCE of the JVM however isn't.

On a project of that scale, compilers for modern chips would probably optimize the code better than (most) programmers.

Correctness is more important than speed.