I think the Cobalt/Pursuit will fare better... GM obviously recognized the problem with the Cavalier/Sunfire, that's why the new models have been given a new name and a new style. I was very impressed with the fit, finish, and ride of the Pursuit GT, and for the money I think it's a great car.
It's just a matter of getting people into these cars, which shouldn't be hard except that GM has that horrible reputation thanks to Cavalier/Sunfire. So, unfortunately for them, they may have to be selling these cars at a loss in order to "prove their worth".
Assuming GM gets their quality up, once perception has changed they should be able to compete on a level field with Civic et al. It'll take time, and it won't be easy, but the new Cobalt/Pursuit is a much needed step in the right direction.