Goddemet! It really is quite simple:
If you were going to upgrade EITHER your cpu OR your vid card, which should you upgrade in order to play future games?
The Doom3 alpha suggests you should upgrade your cpu, while 3dmark03 suggests you should upgrade your vid card.
Doom3 is a future game, while 3dmark03 is not. Conclusion: Doom3 is a better benchmark to represent future games' performance.
Another example: When UT2003 was released I was running on an Athlon 1133/Geforce DDR rig. 3dmark2001 suggested I should upgrade my vid card in order to play it more effectively. Which I did.
Did it improve my performance? Yes, but only a little. Did it live up to the twofold performance gain that 3dmark2001 suggested? Not by a long shot.
HOWEVER, last week I upgraded my cpu to an AthlonXP 2000. My 3dmarks only went up by about a 1000 points, BUT my UT2003 performance skyrocketed. Meaning that 3dmark2001 is/was a crappy benchmark to represent future (at the time) games.
Even for kicks I put my old Geforce 1 card in my computer. UT2003 runs WAY better on an AthlonXP 2000/Geforce 1 DDR setup than on an Athlon 1133/Ti4200 setup.
Which leads us back to the 3dmark03/Doom3 dilemma: Having checked the alpha I know for a fact that Doom3 will run better on a top of the line cpu with a midrange vid card, than a midrange cpu with a top of the line vid card. 3dmark03 suggests the exact opposite, which is, quite simply, wrong.
It really is as simple as that.
It is the mark of an educated mind to be able to entertain a thought without accepting it.