"Is the Prius such a green car though?" No, it's not.
It's an attempt by car makers to LOOK like they are making more responsible cars while still feeding the oil companies. The money that was spent to develop hybrid technology could have put Hydrogen fuel cell cars on the road in equal numbers to hybrids. The cost one one new oil rig could have paid for the retrofit of stations to add H2 and start making it, which is cheap and easy.
Hydrogen can be made at the station with a solar panel on the canopy. The by-product of making the fuel is oxygen, not toxic chemicals. When you fill your car and drive it, you recombine that oxygen with the on board hydrogen, and get back the water you originally used to make the hydrogen, which is what comes out of the tailpipe. Perfect.
Fuel cell cars also use a permanent ultra capacitor, instead of a huge battery array, because they don't store the power, but generate it. They also use a lot less oil and grease, and what they do use can be made synthetically. Finally, an electric motor also has one moving part, vs. hundreds for an internal combustion, and has more torgue, even at 0 RPMs.
Hybrids are actually keeping the environment polluted longer, since now it will take a lot longer to replace gas and diesel with hydrogen.