I think SQL Server was a little different in that it wasn't quite from scratch, but was a JV that built on existing Sybase code? They eventually went their separate ways, though, and after the split is when MS really started bringing in SQL Server revenue.

I'm impressed with he way the succeeded with different approaches: plenty of homegrown applications, some acquisitions, some joint ventures. Sure, there were plenty of projects that didn't work out, but the ones that did work out did really, really well.