Hi,

Sure it's possible.
Note that you won't get to emulate a very fast emulator, but the point is to get it.
I have a url for a GameBoy emulator written entirely in VB (even the z80 core). Surely it's a lot of math, but...
It runs only one commercial game, due to not emulate a specific chip of GameBoy, but, if it emulates z80...
From now, my interest would be develop a SMS emulator, using DirectX for graphics. Maybe this can help in boosting a little.
It's very good that you're interested in it. We can keep in touch here until we close a development team

Regards

Marcelo Nogueira Magri