I've watched Joel Osteen a couple of times and I don't believe so. Yes I believe that Keith Moore is a false prophet, he's said that the New Testament is not worth reading, he's not Jewish but preaches exclusively out of the Old Testament, and he's said that the prophets are stupid and that he's the smartest pastor out of all of them.
And this is where it gets really outrageous, this is on his website if you want to see it to believe it. He's done fundraisers of his congregation to pay for two private jets and a yacht.
And to answer your question, no wealth doesn't make someone a false prophet. It's not a sin to have money but the bible warns about the love of money is the root of evil. I believe that tithing is important and that you should support your ministry to help spread the gospel.