There is no such thing as a "best" language, without defining exactly what it is you want to do. I've used literally dozens of languages over the last 35 years. All have their strengths and weaknesses, and different languages are good at different things. Even now, I use a number of different languages, depending on what I need to do. On any given day, I might be working in c, c++, c#, Perl, Java, Javscript, HTML, CSS, shell scripts, or any of a half-dozen others.
Since you're on an Arduino forum, I can tell you that if you want to do something with Arduinos, very nearly your only choice is c++. Whether that is "best" or not, it IS what is available, and it will get the job done.
Regards,
Ray L.