Hello Geoffrey, and welcome to the forum.
Well, thet fact that you're dealing with grub2 tells us that you have F15 or higher, but when posting for help, it is greatly helpful to the folks who might offer help if you would also mention which specific release of Fedora you're dealing with.
If you added a line "#GRUB_GFXMODE=some_resolution
" to the /etc/default/grub file, two things:
1) Beginning a line with "#" makes it a comment line, which is ignored.
The line needs to be "GRUB_GFXMODE=some_resolution
", without the leading # character.
2) Any edits to the /etc/default/grub file are not activated until after
you then run, as root:
grub2-mkconfig -o /boot/grub2/grub.cfg
The actual grub2 config file settings are in /boot/grub2/grub.cfg. Running the grub2-mkconfig command as shown above reads the entries in /etc/default/grub and applies them to the /boot/grub2/grub.cfg file. It also runs all the scripts in the /etc/grub.d/ directory.
Also, you do not necessarily need to attempt (and probably shouldn't) to make your grub2 menu screen jump to the full native resolution of your LCD monitor. Something smaller will work just as well. My LCD monitor has a native resolution 1920x1080, but in my /etc/default/grub file, my entry is this:
Even with a smaller than "native" resolution, 1440x900 requires using a larger font size, otherwise the font would appear tiny. the "x16" part is optional, and sets the color bit depth (it could be 8, 16, 24 or 32).
Once you boot into your desktop session, your session can set the final graphics resolution to use.