Games appear to be a mixed bag. The fancier the game, the less well behaved it appears to be.
The Deus Ex demo off the net ran a little sluggish and the mouse and on screen cursor appeared to be out of sync. Also, it became fairly unusable after my dock suddenly popped up in front of it.
Unreal was even more choppy and the main menu did not show it's text on screen.
On the bright side, I tried out a couple of my old console game emulators dgen and snesX and they both SERIOUSLY out performed themselves under Os 9. Under Os 9 they had just barely been able to run my games at a fairly acceptable speed. Under OS X they suddenly appeared to be running like a full speed console. I could not see any dropped frames from my little blue/white g3.
AlephOne (marathon) does not work with OpenGL turned on , but it runs with the old software rendering turned on .
I haven't had any trouble with my old 2d games.
Eric's Ultimate Solitaire works fine, as does RealmZ.
The old Doom2 seems to work ok as well , though I couldnt get the carbonized version of the app to run at all .
These are the only games I have tested so far under OS X. I'm not terribly surprised that my 3d games would have some trouble. They are probably trying to access openGL hardware directly. Either that or they might be trying to use the old Connex open gl software rendering under classic. I'm not sure.