It's hard to say who is the "richest"(in monetary terms) Nepali in the world but here are some names I have heard/read about

*Dr. Upendra Mahato  from Russia (often referred to as the richest Nepali in the world)
* Aditya Jha from Canada (I have heard of him being referred to as the richest Nepali in North America...I am not sure if he is Nepali or not)
*Shesh Ghale from Australia (I have heard of him being referred to as the richest Nepali in Australia)
*Balram Chainrai from Hongkong ( was in news recently for buying a English Premier League Club..not sure if he counts as a 'Nepali' though)
*As far as the richest Nepali in U.S. goes, there are a lot of people who are referred to as the richest Nepali in the U.S. This is because there are quite a few Nepalese who have managed to own businesses and are millionaires. The people in these states claim that the Nepali millionaire there is the richest Nepali in the U.S. Haven't heard of any Nepali billionaires in the U.S. (may be in 20-40 years)
*I read somewhere that according to the taxes filed, Khetan group of industries makes the most money in Nepal. Some of the Golcha, Khetan, Choudary, Shah and Rana family members are considered to be the richest Nepalese living in Nepal (and may be even some of the people who have been ministers/prime ministers a lot of times)
 

--Hopefully some of us here in sajha can become the 'Vikram Pandit' of Nepal in 20-30 years--