It depends. I'm definitely biased towards some brands, but I would never blindly buy a product out of loyalty.
Fractal Design makes my favorite cases, and I have used a Fractal Design case in every build that I have made for myself. I like their design language, their durability, and their emphasis on silence. However, I know that there are other good options too, and I always do research before purchasing. I definitely have a bias towards them though.
I had a Noctua cooler on my old build (an i5-4690K overclocked to high heaven), and it worked wonderfully. I hated the aesthetic of the brown fan though, and am happy to see that they now make other colors. That being said, my current build uses a basic Cooler Master Hyper 212 Black, because a Noctua is overkill for a Ryzen 3600 that just sips power. When I do a custom loop in the future with a 12-core or 16-core Ryzen, I'll probably opt for Noctua fans on the radiators. I have a bias towards Noctua as well, but not exclusively.
I had an EVGA GPU in my old build, and it was reliable and worked well. I did like their older design language compared to their newer, less "solid"-looking designs. My current build uses an older EVGA PSU that has better OEM components than their newer models (this is a trend that I'm seeing with Corsair's newer PSUs too unfortunately). I wouldn't hesitate to recommend most EVGA products simply for their customer service and reliability.
Gigabyte has never given me any problems either, but I have heard more problematic anecdotes with them. Generally though, it seems that their higher-tier hardware in particular is good quality and reliable. I built a PC for someone with a Gigabyte board, I have used their ITX boards exclusively, and my current Gigabyte GPU is very quiet and has a nice backplate.
I like MSI, especially their motherboards. They don't skimp on stuff like power delivery, networking, and audio circuitry on their mid tier boards either, which I appreciate.
AMD: ahh, the underdog! I remember buying a laptop with an A10-4600M APU years ago that only recently died. For my workstations though, I have gone Intel (for obvious reasons) until my most recent build. Though I understand their reasons for not supporting 4th-gen Ryzen on B450, I'm still pretty miffed about it. That's the thing about duopolies - AMD or Intel will always have an underdog/overdog relationship, and as either company pulls farther ahead of the competition, the incentives for them to cater to consumers will wane.
Dell: I like their monitors, have owned Samsung monitors in the past too but I would pick a Dell monitor over most other brands. I am eyeing a refreshed XPS 13 or 15 in the near future, those things look amazing. Just hope that they release Ryzen 4000-based models soon.