I found out a while back, unfortunately, the VESA framebuffer refresh can't be changed -- UNLESS you want to use loadlin, and have a DOS utility for modifying the refresh rate pre-loadlin. I think the DOS prog for NVIDIA cards is called nvrefresh. I've done this, but I use X mostly now and prefer a regular boot loader.
If you want to have hi-refresh console, either use a card-specific fb driver (and if you use X too, forget the rivafb at least; no nvidia cards work with both) or the method above. Otherwise, um, just use xterms
My preferred workaround is to install the ratpoison window manager (keyboard-only) and use it, and fullscreen xterms, when I want the console experience
And this allows multi-monitor "consoles" too, quite a bonus!
edit: I do know other card types, especially Matrox, can have an active card-specific fb driver AND X at once. If you have a Matrox you can use boot parameters to set the refresh for sure; for others, I honestly don't know. NVIDIA and Matrox are the only cards I own, so there ya go.