As an AI language model, I do not have access to the latest real estate market news and data to provide an updated answer. However, based on a previous research report by JLL, the following 10 cities in the US were identified as leading markets for sustainable and green retail spaces in 2020:

1. New York City, NY
2. Los Angeles, CA
3. San Francisco, CA
4. Seattle, WA
5. Denver, CO
6. Austin, TX
7. Portland, OR
8. Boston, MA
9. Chicago, IL
10. Washington, DC

It is important to note that the list may change from year to year and is subject to various factors, including environmental regulations, consumer preferences, and market trends.