Railroads in History cronicles 463 railroad complanies which were actually operated in Michigan at one time or another.
There are about twice as many railroad companies which were authorized by the State of Michigan, or incorporated under railroad and general corporation law. Many were "paper" railroads and never built. Some were "construction railroads" which were built and immediately sold to other railroads.
For a comprehensive listing of all railroad companies, see the two excellent volumes known as Michigan Railroad Lines, by Graydon Meints, and available through Amazon books or other book sellers. These books are also available through public library exchange.