What's most Important to you when choosing a Job ? Select anyone! 1-Good salary 2-Better Company 3-Good Boss

It is difficult to indicate only one. All of them are important. 

Well, that's a pretty interesting question. In my opinion, I think what matters is taking a further look and start thinking about how the job will start to feel like and become later on. At first, many people tend to act in the spur of the moment and choose  a job thinking that is rewarding and fun. However, when they spend some time they start either feeling generally bored of the routine or not feeling that the salary covers their needs. You need to specify some time to evaluate the choices, a discussion with your peers, family, or experts would make you feel even better. In brief, you need to think nice and slowly to have the best of both world. 

I would be choosing a Job in Better Company,  If company is good then all its process, policies, and business strategies are highly standardize;  normally they will focus on high vision with long term business goals which definitely required career growth, safety, health and environment; employees feedback and employees suggestions etc. 

Option for the Good Boss we cannot judge at the time of joining so we are not 100% sure.  So this option doesn't really work for job selection.