Your point is absolutely correct, but your example could be better IMO. It's not fair to compare a desktop chip with 45W TDP with a laptop chip rated at 35W. Not to mention that the newer i7 actually goes up to 3.7Ghz turbo (vs. 2.5Ghz constant for the C2D) for single threaded loads, so the clock rate is not really comparable in that benchmark (even though base clocks are the same).
A better example would be C2D E8600 @ 3.33Ghz and i5 3470S @ 2.90GHz (3.6Ghz turbo). They are both 65W desktop parts, and the single threaded clock speed is similar. You can see that the C2D gets 1,376 in the single threaded benchmark, while the i5 gets 1,874. The difference is not as drastic (the C2D launched at a significantly higher price point as an enthusiast level chip, while the i5 is a budget chip) but definitely still significant. There are probably even better comparisons but I didn't spend too much time picking out comparable CPUs from different generations.
True, good point. I tried to find something with a similar nominal clock speed and forgot about Turbo. But then, Turbo is a good example why single threaded performance is getting better even in the age of multicores.
A better example would be C2D E8600 @ 3.33Ghz and i5 3470S @ 2.90GHz (3.6Ghz turbo). They are both 65W desktop parts, and the single threaded clock speed is similar. You can see that the C2D gets 1,376 in the single threaded benchmark, while the i5 gets 1,874. The difference is not as drastic (the C2D launched at a significantly higher price point as an enthusiast level chip, while the i5 is a budget chip) but definitely still significant. There are probably even better comparisons but I didn't spend too much time picking out comparable CPUs from different generations.