Do all Jettas have a rougher ride?

for a COMPACT car they actually are one of the better riding cars... but you are comparing them to fullsize cars and one in the luxury realm. there is no car in that compact class that will give you the ride (wallowing) of the cars that you ask about. on the other hand, there's nothing in the class of cars you ask about that will cost as little or get the fuel economy of a compact class car.

as an aside, jettas are notoriously unreliable.

you did not state the year of the jetta, i owned a rabbit, an 84 jetta and an 84 vanagon and felt all cars were quite quiet except fot the front doors which i used a lot of sound deadning material and other tricks to quiet the ride for my car audio system.

many german cars are built with stiff suspentions compared to american cars and i found using kyg struts and shocks complemented the stiff ride, feeling the steering is good unless it is rough but my experience is you can feel what is going on.

as was said tires make a huge difference as well as bushings and ball joints, if the wheel bearings have not been repacked for a long time (or ever) that can make things seem rough, it could be out of alignment.

like i said german suspentions are stiffer

Tires matter a lot. You want radials. They are a softer, quieter ride. Sounds like hers were bias ply and pumped up hard. Use recommended pressure the car manufacturer has in the glove compartment? sticker. All tires say 32 PSI regardless of the car you are putting it on. But all cars have different weights and is distributed differently.

As for radial brand, I like Michelin. Seems the nicest ride and longest lasting tire.