Canon VS SONY VS Nikon. Which brand is best in D SLR's Camera?

Canon VS SONY VS Nikon
Also please give reasons for it.

Sony

Canon is the best DSLR company for camera.

I prefer Pentax, but you'll have to handle them to find out.

Buying a camera is all down to a) what you want it to do in terms of means of taking the picture (how many different ways you can take a pic) and b) how much do you want to pay?

Sony bought out Minolta, and in their day, all 3 had good names. They still do, but now comes the money bit. Look at the specs and reviews of any 3 cameras, 1 each from the 3 names, and then look at price comparisons between them. If one is up to 20% cheaper than the other 2 for what's on offer, then you have to decide whether you want a top name like Nikon and Canon (not a lot of difference when you look at the top end of the market) or save a packet by going for Sony. To use an old adage: cut your suit according to your cloth. My personal choice would be Nikon, although back in the day, I was originally a Canon man. I just couldn't get on with the Canon EOS system and the fact that they changed the lens system to accommodate the new designs etc.

Nikon

It is all down to personal preference
Handle each one, look at the accessories available, look at the functions of each one then decide which is best for you.

They all make good cameras (add Pentax to your 3)

The H is the industry-standard and is the best. The brands you mentioned are the most popular ones with the C's and N's lording it over in the market. The S's are relatively new but very stylish. You forgot to mention the P's which is actually as old as the two most popular brands and is a very recognizable one if you ask veteran photographers. The P's also make medium format dSLR's like the H's and the M's. When it comes to lenses though, no one can beat the L's.

All are good and have their strong and weak points, depending upon your personal needs and viewpoint. A bit or trivia, Nikon's DSLR sensors are made by Sony. It may come down to how the camera feels in your hands. Physically, it seems that Sony is the smallest and Canon is the largest. My hands are rather large and I've used a new Sony mirrorless and it's just too small for my hands. I can use it but it's just not that comfortable. You'd think the Canon would fit me the best, but the location of the shutter button cramps my finger after a while. Nikon seems to fit me the best. You might go to a store with all three brands and handle them with your eyes closed. Don't drop them! But with your eyes closed, see how the grip fits your hand, the location of the shutter button and focusing and zoom ring and so on. Your eyes will influence how something feels, closing your eyes means you have to depend upon feel alone. Just like doing sheet metal body work on a car. I know from experience that with your eyes open, often times you can't feel a slight imperfection in the metal surface. Close your eyes and you can then feel it. Not sure why, but it works.

An advantage Nikon has is that you can use any lens built in the last 40+ years. You may have to operate them manually, but cou can use them. Some of the old lenses have some really great optics. You can also use old 3rd party lenses having the Nikon mount. Lenses like Vivitar were made by reputable firms such as Konica and Tosina. When Canon went digital, they changed the lens mount, meaning you can't use the old film lenses. Sony can use many of the older Minolta lenses, several of which also had great optics. This means that with Nikon or Sony, you could buy some older used lenses on ebay. If you decide you don't like that type of lens, you're out a small amount of money. Nothing worse than paying big bucks for a lens you find doesn't suit your needs.

Cannon- easiest camera to use, good if you don't know how to work the advanced settings of cameras
Nikon- generally has highest reviews for picture quality, harder to use, but once you get the hang of it the pictures will look the best
Sony- inbetween the 2
It really matters if you value ease, performance, or a bit of both