OP: I went through this same exercise. See old thread here:
Best DOS video card?
Even though I decided upon the Matrox G400 card then, which I still have, I changed it over to a Voodoo 3 3000. It has great 2D quality (like the Matrox), fast DOS support and VBE 3.0. There are some very old games that don't work with it, but those usually required a specific card like S3, Tseng, Paradise, etc if they don't have VESA support. Any game that old can run in DOSBox, so to me a good *later* mode DOS machine + Win98 was more important.
If all you care about is DOS, DOS and DOS, then the S3 Trio64 or Virge variants were the best. If that's *too* old for you, or you must have an AGP card over PCI, then the Voodoo 3, 4 or 5's are good, and have Win9x drivers to boot. If you must have Win 3.1, then the S3 or the Matrox G400 may be a good choice. If you are looking for a 486 era DOS machine with ISA or VLB, then the Tseng ET4000 series were very good. I owned several Diamond Speedstars back then.
Sorry, I know others will recommend an early model NVidia board, but I cannot. Fast, but worst clarity of any board to date that I have ever used. ATI's were equally problematic. Funny how times have changed.