PC software for FPGA control through USB port

I would immediately follow the ethernet suggestion, with a compact and flexible hardware ethernet stack available as a Megafunction or third party IP. It seems to me, that ethernet is used now almost exclusively by embedded processor applications. Or did I miss something?

USB with FTDI chips doesn't require driver programming, at least for Windows and popular Linux OS. The existing driver can be interfaced at the application level with a few lines of code. But it doesn't provide the rich choice of communication options as ethernet, so I basically share your preference.