The Ludlum estate is merely milking a cash cow. Some of the 'ghost written' Bourne novels are OK, some are trash. I have given up on them.
I gave up on Parker long before he died, he had become the very definition of 'formulaic'. It's the rare writer who can turn out multiple books based on the same character and premise and still keep each one fresh and entertaining. Those who can and do pull it off are Child, Burke, and Sanderson, to name a few at the top of their game. With those guys, I await each new volume with keen anticipation, savor each page, and regret it has to end.
I find myself really liking George Pelicanos too, for his gritty portrayal of the streets of Washington, D.C.- 20 minutes and a whole lifetime from where I live.