I think that over time Matrox just focused purely on driver stability as opposed to performance, as they sold (and still do sell!) these cards for basic display systems, such as signage and basic dual display output. Under Windows XP, I found that the whilst the 5.93.009 drivers are the last to offer Direct3D support, they cannot render into textures, causing 3Dmark 2001 to refuse to run! The previous 5.92.006 drivers do work, but I would be very interested to see how much better even earlier drivers perform.
Actually, the last driver under XP that supported D3D for the G4x0 series is 5.96.004. I keep a copy of it on my storage drive for this very reason. It's the last version viable for gaming and since I own a number of G4x0 cards as well as a G200, I keep it around.
edit... I just looked at Matrox's website, there's three different versions of the 5.96.004 driver. One, which I've never seen until today, explicitly states that it doesn't support D3D. It's dated Jun. 29, 2006. Of the other two, one is the WHQL version also dated June 29th, 2006 and the third one is dated May 8, 2006. I have no idea which one I have, but I've been using this exact same file since sometime in 2006 (I have a CD backup with it on there as well). I've run the version I have with plenty of games, from Unreal and UT99, to all manner of old games, demos of games, etc all of which use D3D.
This thread has me ready to yank the Radeon 7000 out of my P3 just to install my PCI G450 Dual Head card just to run Quake 3... And I'll do it tonight if anyone can point me to a how-to to get timedemos back. (I have the Linux Q3A, but using ID's instructions to get it to run under Windows. Just install the point release for Windows and copy PAK0.pak to base3A). I'll also install Unreal on it and take screenshots just to show it running D3D.