This is a long standing question and the subject of never-ending debate. Everyone has an opinion and most are valid. In the days of 35mm photography the frontrunners were Canon and Nikon for many years joined by Pentax, Olympus and Minolta. When digital technology started to supplant film, Canon and Nikon developed their entries with Nikon joining up with both Kodak and Fuji to provide not only choice, but also technologicl innovation. Sony bought Minolta and the race for superiority was on! But behind the scenes, Sony was supplying digital sensors to almost everyone. For most of the first 10 years, there were 2 kinds of digital cameras: professional quality DSLR's and consumer directed "Point and Shoot"s.
Then Olympus, Panasonic and Leica co-operated to develop the "Four Thirds" format and then the whole business took a left turn when the Compact System or "mirror-less" cameras were introduced. (I am not even going to mention the camera in your cell phone!!)
Today, buying a camera is a very complicated process and you need either a strong background in photography or a sales professional you can trust. The best camera is the one that YOU can use properly to capture the images that YOU are happy with. Nothing else matters.