I used to do a ton of 3DMark2001 benchmarking back in the day. It's a great single-threaded CPU test, and yeah...Core 2 is well over twice as fast as Netburst clock-for-clock.
Here's a Core 2 Quad Q6700 overclocked to 4GHz with a GTX 680:
And here's a Pentium D 935, also overclocked to 4GHz. Yeah, it's using a GTX 560, but the 3DMark01 Game Tests are completely CPU limited (the overall score doesn't take any of the synthetic GPU tests into account).
And just for fun, here's my DDR-equipped PIII @ 1575MHz with a 6800GT GPU, managing to outperform a Northwood P4 @ 2.4GHz with a 7800GS GPU!
And some other scores, all under WinXP:
Celeron 2.6GHz (Northwood-128, GeForce 7800GS): 9099
- that's no typo. Netburst with only 128K of L2 really is that slow.
Pentium M Dothan @ 2.72GHz (GTX 560): 43639
Opteron 185 (Socket 939) @ 3.13GHz (GTX 560): 47464
Core Duo (Yonah) @ 3.08GHz (GTX 560): 50329
Core i5 4670K @ 4.5GHz (GTX 680): 117447