Java programs need to run on top of JVM no? So if it uses the same algorithm. It should run slower on a machine?

Program langauge is just syntax. But different compiler interept code differently and create somewhat different machine code. So it does affect the speed somewhat?? But it might have to do more with compiler and not the program language.

I understand what you are trying to say. Using which ever program laugauge probably won't matter much. Program language is just a tool.

I think it have to do more with standard. It makes people's life easier. Code reuse, library, learning curve, and habit is what stick people to use whatever language they use.

Unless people can find drastic improvment on using one language instead of the other. People won't find the need to change.

While it's true the interpreting byte code process done by the JVM is unlikely to beat natively compiled C or C++ code, the speed gap is getting smaller now that the inner JIT compilers are getting more and more efficient.
Right, different compilers interpret the source differently and produce various quality of code. The gnu compilers, the most widely used, can be beaten by other compilers targeted to a narrower architecture and O/S
Speed also has to do with the programming language, some mathematical algorithms are still processed faster in fortran that in C. Anyway, if you really want the highest possible speed, nothing can beat assembler, but you loose portability.