I know this will probably be a limiting question in a country the size of China, but I would value your opinions. Thank you.

????

I think it really depends on your interest. Other than Beijing, there's really no "must see" for a tourist, in my opinion. Similar situation to the US.

For example, Shanghai is a must see if you like modern buildings and skyscrapers. But definitely not worth visiting if you don't like new stuff.

Or Dunhuang/Silkroad is quite exotic, but one has little interest in religious arts or history, then it's a bore. Even if you like natural scenery, you can probably find similar in the western U.S.

Or like the high-elevation national parks of Huanglong/Juizhaigou. Its beauty is incredible and quite unique in China, but you can also find similar in Yellowstone and the Tetons. It's also hard to get to, with questionable facility. So, is it a "must see"? Depends.

OK, a bit narrower focus. Must see of religious significance and must see of historical significance older than 500 years. ?? How about gastronomical significance, now thats a question.

Religious and historical significance... I'd do this:

1. Beijing
2. Chengde (about 4 hours by train NE of Beijing). The temples there are <500 years old (about 300), but are magnificent and significant.
3. Wutaishan (5 Plateau/Platform Mountain) in Shanxi province, west of Beijing.
4. Xi'an
5. Luoyang, in Henang Province. Another old capital of China. Visit the nearby Longmen Grotto (from 5thC A.D.) and a little further away, Shaolin Temple.
6. Silkroad tour from Lanzhou to Dunhuang.

Okay, so that's six...

I can answer only based on my travel experience but here are my recommendations in no particular order.

1. Great Wall - not the touristy part
2. Beijing - Forbidden City, Summer Palace, etc.
3. Xi'an - Teracotta Warriors
4. Shanghai - The Bund, Jin Mao Building
5. Hong Kong

Have fun!

Thats what I am after ...peoples real experiences ! Thank you...any more!

The answer also depend on whether you think this will be your only trip to China. I agree with Beijing : Forbidden City and Summer Palace, Xian, Shanghai. I don't agree that Shanghai is only new buildings. If you wander the city, you get the feeling of many different eras in China, and the Shanghai museum is psectacular. I would skip Hong Kong. What you also need to add in is some smaller city with preserved buildings: Suzhou, Wuzhen or others. The silk road is wonderful, and gives a view of an entirely different culture in China, but unless you have endless time, you can't see the big cities and the silk road. If you plan many trips, then you can separate out the areas, and I would start with the biggies listed above. Whatever you do, please try to build in some time to just wander through the cities off the main streets. It's there that you feel the "pulse of the people".

This will be the first trip, who can tell if it will be the last.

Based on my visit:
- Great Wall (even the touristy part)
- Forbidden City
- Summer Palace
- Terracotta warriors
- the peaks and clouds of Yellow Mountain (if you're lucky enough to be there during good weather)

I'd love to see silk road and other parts of China. perhaps next time.

I've seen much of China. I would say

Great Wall Simatai/Jinsinglan
Summer Palace
(Forbidden City is overated in my opinion)
Chengde
Teracotta Warriors
Li Jiang cruise

I would add a boat trip down the Yangtze from Chungching through the three gorges.

any thoughts on Shanghai instead of Hong Kong ?