The first Priuses were stubby and nondescript. They might be considered a proof-of-concept design rather than a car more closely tailored to the automobile market.
It was the second-generation Prius that defined the brand. Its body was given thorough wind tunnel testing that resulted in a basic shape that remains little changed. What has changed over time are secondary, ornamental details. The most recent Prius is a victim of Toyota's recent new styling policy moving from bland to ostentatious appearance for its various car and SUV models.
The comparative-image sets below have the second-generation (2004) Prius at the top followed by third generation (2010) and current (2016) generation examples.
As I mentioned in the post linked above, the nose of the car is poorly related to the rest of the body.
Front Quarter Views
The second-generation Prius was a simple, clean design. It was followed by a design with details giving the car a stronger wedge-shaped look than its basic shape actually warrented. This can be seen in the treatment of the side windows and the character crease below their sills. Current Priuses are decorated by fashionable spikes and other angular treatments of light assemblies, air openings and sheet metal in general. One result is a return to the first-generation Prius' defect of the front end not being very well related to the rest of the car, a problem not found in generations two and three.
Profiles of Priuses have changed subtly over the last three generations. The second-generation car had a lower hood line and no aerodynamic spoiler at the rear. The hood was raised for the third-generation car, probably in response to European regulations. The current Prius has a rear spoiler as well as the Euro hood line. Another difference is the roof curve. Second and fourth generation cars have the roof peaking near the driver's head, whereas the third-generation cars have the high point noticeably farther aft.
Rear Quarter Views
Rear styling of second and third generation Priuses can be characterized as basically functional, though the second-generation car is more successful in this regard. Current Priuses have highly contrived rear-end detailing. The spiky tail light assemblies seem to dictate the body sculpting rather than the reverse. So far as I am concerned, Prius styling is now a fashionable mess.