Out of the three you listed, I'd go in order of . . .

1) Camry - It's boring, yes, but you'd be hard pressed to find a family sedan with a better track record. If you're the kind of person who likes to keep your cars for a long period of time, it'll last you as long as you'd expect and maybe then some. Just don't slack on the maintenance because it's a Toyota. You still gotta take care of it. Don't worry about not getting the hybrid though, you'll still get good gas mileage.

2) Mazda 3 - Kind of interesting that you're looking at two mid-size sedans and then have a compact as your third option. Still, it's not a bad choice. It's attractive, gets good gas mileage, and while Mazda isn't as well known for reliability as Toyota and Honda are, they're better than Mitsubishi. Don't hesitate to look at the Mazda 6 either, as it's in the same class as your other two options. Still, I'd really recommend the Camry.

3) Malibu - Hmm. Eh. Well, are you sure you wouldn't rather look at a Kia Optima or Honda Accord first? I mean, don't get me wrong, the new Malibus and Impalas are much better this time around, but you can get better for your money.