i was always wondering how big the influence of the cpu on 3d performance is,
and how to choose the cpu so it doesn't limit the gpu.

this might be especially interesting when building a dell laptop, where the prices
for gpu/cpu upgrades are MUCH higher than in a desktop, so you should think
well before spending 500 euro to make the cpu 2.8 instead of 2.4 ghz

finally i found an interesting page, where they check different benchmarks & games
using not only different gpus, but also different cpus.
they use desktop cpus/gpus, but the relations should be the same. and the desktop
cpus behave very similar to the laptop ones imo.

the conclusion is, you don't really need the fastest cpu, often a 2ghz core2duo
performs similar to a 3ghz one.

here the benchmark with unreal tournament 3 (with 8800gtx).
the game gives you the same fps, whether you have a 1.6ghz or a 3ghz cpu.
limiting factor is the gpu:

http://www.legionhardware.com/document.php?id=693&p=8

here is crysis (8800gtx). upgrading the cpu from 2.33ghz to 3.0ghz only gives
you 3 more fps:

http://www.legionhardware.com/document.php?id=698&p=6

bioshock. an amd athlon 64x2 4000+ (2.0ghz) only gives you 3 fps less than
a core2duo e6850 (3.0ghz) when using a 8800gtx

http://www.legionhardware.com/document.php?id=681&p=10

a c2d e6300@1.86ghz performs almost the same like the e6700@2.66ghz (with a 8800gtx)
in world in conflict.

http://www.legionhardware.com/document.php?id=676&p=8

medal of honor airborne being most cpu dependent still only differs by 5fps
when you choose a 3.0ghz instead of a 2.33ghz core2duo cpu.

http://www.legionhardware.com/document.php?id=683&p=3

the benchmarks show, that that if you have a core 2 duo cpu with around 2.4 ghz
it should be enough to run your desktop 8800gtx without bottlenecking it in actual
applications (syntetical benchmarks might be a different thing).
so if you have a cpu like this, it should be also more than enough for ANY laptop gpu,
as in terms of performance the 8800mGTX is rather close to the desktop 8800gts
than to the gtx.

True but it all depends on the engine used. Granted you have shown many games that are not heavily CPU-dependent or at least are GPU-bound. However, if I recall correctly, when the source engine was first released it was CPU-dependent. Just giving a comparison however this is only from my memory.

you're right, source engine stresses the cpu more.
there's a test with team fortress 2 on this page showing this as well.
however, source engine is kind of old now and not that demanding
anyway.
i guess upcoming games will be more like the ones listed above
(unreal3, cod4, ...) and stress mostly the gpu.