There is a tremendous quality difference between the well-known brands of Japanese bikes and the Chinese bikes.
The no-name China bikes are a tough call, particularly for a new rider. This is because they are often delivered needing work, and people new to motorcycling rarely know how to do the work themselves. In addition, parts can be difficult to source, and the typical novice is not capable of fabricating parts when necessary. That said, the Chinese bikes, when they work, provide a low cost introduction to motorcycling and a cheap way to see if the sport is for you.
If you search on the popular internet message boards, you will find lots of threads about the China bikes. My take on them is that for an experienced tinkerer, they can be fun. However, if you want a bike to ride rather than work on, you should probably stick with the Japanese bikes. With a relatively new Japanese bike, you'll be able to get a service manual, there will be professional mechanics who can work on them, and you will be able to get parts.
If you are even considering a Chinese bike, I assume you are looking for a play bike that will never (or at least rarely) see a track. In that case, look at used XR200s. They are usually available for less than $2 grand and have an excellent reputation for reliability and longevity. Also look for used CRF150s, CRF230s, Yamaha TTR 225s and 230s. Any of these bikes should be available used for a price similar to a new Chinese bike, and they are a safer bet in terms of being durable and reliable.