Ranking of banks can be done using a number of different measures. These usually come up with different results, both because some banks use reporting methods that have to conform with their own countries’ regulations, and also because ranking of banks by total assets compared to total market capitalization is using a different pool of available banks. Market capitalization is only relevant where the bank is listed on a stock exchange, and several banks are wholly-owned subsidiaries of global financial enterprises and so do not themselves have a share price.
Finding the top 5 banks in the world by revenue may lead to a slightly confusing result. Of the top 5, 4 are from China! The concentration of Chinese banking into giant entities that are basically a government-controlled extension of the finance ministry means that many global banks are being left off this list even though they have a greater impact on the world economy. As well, the Chinese banks that head most lists are highly specialized, active in one field only, such as agriculture or construction. If you leave-off the Chinese banks, then of the top 5 banks in the world by revenue are 3 from USA and ranking next comes one each from Brazil, Spain and UK.
To measure how rich a bank is, analysts usually measure the bank’s net asset value, which means deducting outstanding debt and borrowing from the assets owned. In this method the top 5 richest banks in the world, leaving off the same four Chinese banks, list three from Japan and one each from USA and France. This is largely because Japanese banks are highly structured and very conservative.