Of course this ranking is only based on absolute fuel economy, not fuel economy per passenger (which the Insight would fail miserably, that's for sure).

the figures are MPG city/highway, US EPA estimate (which are usually overstated quite a bit)

20MPG = 8.47km/L
30MPG = 12.7km/L
60MPG = 25.4km/L

1. Honda Insight, 60/66
2. Toyota Prius, 60/55
3. Honda Civic GX (natural gas), 28/39
4. Toyota Camry Hybrid, 40/38
5. Toyota Yaris hatch/sedan, 34/40
6. VW New Beetle diesel, 37/44
7. Toyota Corolla, 32/41
8. Honda Fit, 33/38
9. VW Jetta diesel, 36/41
10. Ford Escape Hybrid and scion xA, 32/37

What's surprising is that the 6-year old Toyota Corolla (1.8L engine) is on the list at all, and that it gets better mileage than the Fit. But i think US Fits don't come with the 1.3L i-DSi or the CVT. But for the Corolla, quoted city is 32mpg or 13.55km/L.