Doom 3 timedemo 1, F.E.A.R. has a in game benchmark tool, Quake 3 timedemo 1. Can't think of anything else right now.

Unreal Tournament 2004
There is a good benchmarking tool for that called Umark.

Splinter Cell: Chaos Theory also has a timedemo benchmark.

I never tried, but you can probably timedemos with Call of Duty 1-2-4, those are also Quake 3 engine games.

Probably Quake 4 too, I forgot to check when I was testing with it.

Half-Life 2 is probably a must have. The current Steam version is DRM free, but it's on an updated engine.

Also, any game where you can reliably reproduce the same game play scenarios. You can find a couple of games I tested here.

Crysis (low settings), Trackmania Nations Forever, Serious Sam 2

Good ideas, also upon looking at some prices, and comparing specs, I think I'm going to look for a 754 PCIe board so i can use the same Athlon 64 3200 and 1gb of ram, but save myself money with getting the cheaper pcie versions of said cards, it should still be a fairly even comparison, because from what I've seen AGP and PCIe cards basically tie each other with the exception of the 6600GT having 100mhz on the PCIe versions ram for some reason over the AGP version.

It depends on the settings you want to use, but for the most part the cards you selected are good in games up to 2004 at most at low resolutions! If you select maximum in game settings - that means all options activated and the highest setting selected none of them can run any major title from 2005 onward comfortably and also most of the 2004 ones. A common occurrence in period correct reviews done by various hardware sites is the fact they did not actually run the games at maximum settings; there were always some settings deactivated or turned down.
Example:
i have the following system: Athlon 64 3400 Venice; 2*1gb ram; geforce 7900gs 512mb. Most people believe that the video card is bottle necked by the processor, however in my testing it is actually the opposite. Game tested: Doom 3 max settings: 1600*1200 Vsync deactivated, all other options turned all the way up. Frame rate is in the high 20's most of the time, during heated combat with smoke or explosions in the low 20s. AA must be brought down to 2X in order for the game to be playable!
This is true not only for the 2003-2005 period but also for the years before and after. I found that generally you need a top of the line video card 1 or 2 generation later in order to play a particular game that was launched in a certain year at max settings and highest supported resolution - that is for a 2004 game you need a 2006 video card, for a 2003 game you need a 2005 video card and so on. There are also exceptions when even a top of the line video card from 3 generations later is still not enough to play certain games at max settings.

Halo: Combat Evolved