Only countries with historically low rates of immigration to the US are eligible for the DV lottery. The full list of eligible countries can be found on the U.S State Department website.
Countries that have had over 50,000 citizens immigrate to the US during the last 5 years are not eligible, ineligible countries include Bangladesh, Brazil, Canada, China (including Hong Kong SAR), Colombia, Dominican Republic, El Salvador, Guatemala, Haiti, Honduras, India, Jamaica, Mexico, Nigeria, Pakistan, Philippines, South Korea, United Kingdom (except Northern Ireland) and its dependent territories, and Vietnam.