No. There are three errors.
First, the millionaire analogy is not useful because some people are millionaires because they inherited money, others won the lottery, others invested wisely in stocks and bonds, other got lucky investing in companies, other built their own business, others committed crimes to get their money, others used talent in some field to become successful, etc, etc.
Second, for the analogy to be relevant to this discussion, then you would have to try to find common traits among people who are NOT millionaires. That's what atheists have in common, they are simply NOT something else that is clearly defined.
Third, the analogy is not useful because people can easily go back and forth between atheist and believer much more easily than people can go back and forth between millionaire and non-millionaire. also, 99.99% of everyone who is not a millionaire wants to be a millionaire.