I am of Chinese origin and I might be slightly critical but I will be honest with you. I have even been to China twice to visit my parents village and I work in a Chinese neighborhood. I might get downvoted but whatever.

Here is a short list of what many Chinese-Americans think about people from China (please do not get mad, I know this does not apply to everyone!):

They always push themselves into you. Getting off the train can be hard or impossible sometimes.
They think about themselves and are very materialistic. It is always about money and showing off your wealth (like in some weddings they read how much you give to the bride&groom so if you give too little, you look bad).
Everything is so fake to me because parents are always trying to compete with/one up each other. For example, my son is in Harvard where is your son? My son makes 100k a year, how about yours? Do you like my Gucci and Gabbana, my super-rich-doctor-son got it for me? 
People from China tend to bump into you or step on you and do not even say sorry.
They talk so loud on the phone.
They are really good at math.
A lot of them do not pay taxes or try to avoid paying taxes to get government aids.

I get slightly annoyed when people are like "Chinese people are so hardworking, shy and smart" because those people who say this probably only know one to five Chinese people. It is like people saying that Americans are "stupid and fat". Or Italians are "Romantic and sexy". Of course, like I said before, not every person from China is like this! 

Let the downvotes begin.

edit: typos

In Spain everybody usually think that Chinese people are hardworking silent people and very intelligent. We usually have the impression that they are doing lot of things at the same time and talking very quickly. People usually think that they all know or practise martial arts as kung fu, and know misteriour remedies for health.

Everybody is fascinated by their writting system, and Chinese is viewed as the most difficult language in the world. Spanish people usually think that all Asian people (Japanese, Korean, Vietnamese, Thai, etc.) are all Chinese, and usually think that Chinese are the best scientifist of the world. Misconceptions between Japanese and Chinese culture are very often. So, don't be surprised if somebody ask you about your favorite "manga" or if you love karate, sumo, or "dorajakis".

On the bad side, they have the fame of being very greedy, with problems with addictions (videogames, computers, slot machines, and porn) It said that Chinese only think only about money, and they don't are interested about feelings as true love, friendship, social relations, etc.

Hi! I am a Japanese university student and stayed in Hongkong for 8 months.

I have some Mainland and Hogkong friends and I noticed they are different.

For me, as far as fashion, characters and atmosphere, Hongkong people are similar to Japanese people than Mainland people.

Moreover, even Mainland friends, depend on their home cities in large China might affect their characteristics too.

However, in general, people recognize Chinese tourists are rude and having bad manners, I think that's true.

On the other hand, when I look at them individually, they are really nice and feel typical Asian people.

I like them,  but it is more nice when I have deep relations with them.:)

Thank you!

To Ellie:  I can understand what you said. Indeed, those phenomenon that you have said are common in China. People like to compare with others and show off their wealth, I really don't like this. There are a lot of low quality people just like you said, impolite, rude and so on. And there are many "keyboard man " on the Internet.

But anyway, there are still a lot of kind man in China. And you will happy to be friends with them.

Finally, thank you so much for answering my question. Good luck.