Are Whales More Intelligent Than Humans?
The "wiring" of the brain is more important than the actual size. If only size would matter that basically humans would be rather unintelligent beings ( many many animals have larger head and brain than us). Intelligence is more related to the complexity of the brain (number and size of different brain components) and the number of connections between neurons. We humans are intelligent because we have high complexity compared to our brain size, our brain has more grooves therefore higher surface than a whale brain. So even though whales are quite smart they're not as smart as us.

EDIT: After getting a few comments I felt I need to clarify my answer, so here it comes: as pointed out by user137 humans have much higher brain-to-body size ration than whales and this is very important. What I was trying to explain (yet failed for the first time it seems), that mere physical size / volume is not that important. The level of development and complexity is that matters the most. Many parts of the human brain is found in lower order animals as shown in the image below:  (taken from http://en.wikipedia.org/wiki/Brain

The surface to volume ratio matters because the higher ratio implies a more complex brain structure. So while whales have a higher surface in absolute value (approx 2-3 times) yet their brain is larger by approx 5-6 times ( lots of comparison data here), thus we have higher surface/volume ratio (i left the ratio part out on my original answer). In the accepted answer on the question linked by Bez it is said that more grey matter in frontal lobe correlates with IQ. Now since grey matter is made of neuron bodies and (fewer)axons, this is quite straightfoward --> more neurons = more connections = higher complexity. But all that comparison was made between humans. So brain size differences between different individuals of the same species may contribute to individual qualities. Comparing mere physical brain sizes of different species is not straightforward because of different brain development levels and brain structure.