well I can take credit for gensavga.exe, as it was I who modded the original code to work with the avga!

For snes, the job has already been done. I use SNES9X which allows you to set the preferred resolution in the display setup (256x240@16Bit).
The only unfortunate part is that the keys to pause, exit a game etc. used don't match mame or gensagva. I had a look at changing this a while back. Couldn't see exactly where it lived. Nor did I have the compile tools installed to ever get it going. So I kind of lost interest in it there and then. Call me weak!