I did that and was successful to some degree, but it's not easy. I would've done something else if I knew that back then.
I can only imagine that if you create any tool worth competing with SAP, your customers also have to be huge companies.
We lost some customers to SAP later on because they become bigger and "consultants" told them that they should switch to SAP because, you know, all big companies use SAP. I haven't heard of any success stories from those customers yet (this is not entirely SAP's fault though).