On gaming forums, I noticed that the Corsair keyboards are the most often recommended, which is kind of puzzling.
It is not that they are a terrible product, but they are one of the few keyboards brands that have had fairly serious problems and critique on every iteration of their product. The first generation of Corsair keyboards had some hardware and software issues (LEDs dying were a problem, bricking keyboards when upgrading firmware, repeated key problem, generally terrible drivers, not to mention they were not fully mechanical). The second generation of Corsair keyboards are a lot better, but some problems remain. Complaints about LEDs dying are still very common.
If you compare that to some other brands that have been making quality peripherals for years without any serious design issues or specific recurring malfunction, I find it hard to recommend Corsair keyboards over some of the other brands that are available. Their popularity is probably due to their looks, good marketing, and the good name of the Corsair brand.
Another thing to point out, that "gaming keyboards" are really just keyboards. Some of them have specific features that you might want, like macro keys. But most of the features associated with gaming keyboards, like n-key rollover, or media keys, can be found in many decent keyboards. The only real difference is how they look aesthetically, as many people seem to like the bright lights and shiny plastic approach that you usually get with things that are gaming branded.