The first console I've ever owned was a Nintendo Entertainment System. I've grown up with them and I was raised in their style of gaming. For that reason, they'll always be my number one no matter what they do.
Second is Microsoft. During the 7th gen, they packed the Xbox 360 with so many features that were just brand new to me. I've always loved gaming but I also always liked the idea of a console being more than just a games machine--whether it was taking pictures with a psp or watching movies on a PS2. Xbox was the king of bonus stuff and even now is probably my most played machine.
Third is Sony. Part of my still holds a grudge because of how badly they trounced the N64. Still, in 1997 I had no choice but to switch sides and become a PlayStation fan. They revolutionized what gaming could be and their cinematic experiences always touch me. Plus the PSVR is a glimpse into the future of gaming. If the PS4/PS4 Pro still offered better 3rd party experiences than Xbox, it would be really hard to justify having an Xbox One (or four) in my home right now.