NPR posted some interesting graphics comparing the size of the world's biggest economies along with an article entitled The World's Richest Countries and Biggest Economies in 2 Graphics.
The first graphic (below) shows the countries with gross domestic product (GDP) over U.S. $100 billion. The United States is still by far the world's biggest economy in terms of GDP, more than twice that of China which is the 2nd largest. However, China's economy has been growing at a much higher rate than the U.S. over the past few decades and is many economists predict that it will overtake the U.S. within 10-20 years.
The second graphic is a bit more informative in comparing relative wealth between Americans and Chinese (or people from other countries). This one shows countries with per capita GDP of over U.S. $15,000 a year.
If you're looking for China, you won't find it since, despite China's large and still rapidly growing economy, its still a fairly poor country with per capita GDP of about U.S. $7600. I'm not sure if this graphic considers purchasing power parity. If not, its a bit misleading since $7600 can you you much more in China than it can in America. For example, I bought dinner for 2 people (3 Chinese dishes or entrees, unlimited rice and 1 beer) at a simple but decent restaurant last night for 40 RMB (less than U.S. $7). The equivalent in America (if it could be bought at all) would probably be at least $30. This is why, even though Americans are on average much richer than Chinese, I always feel comparatively poor when I return to America.