The models in bold are cars I've experienced firsthand, whether through actually driving or simply riding in for extended periods of time. Lists like these aren't exactly the most balanced way to go about comparing a set of cars, but here goes.
1. Mazda6- I've driven an '06 Mazda6s as well as a friend's '06 Mazdaspeed6. I'm sure my time with the Speed6 influenced my overall impression of the car, but I was impressed with the 6s I drove regardless. Exterior styling is crisp and decidedly sporty, and the interior defies that of the typical ho-hum family sedan in my opinion. The current 6 is no longer the freshest of the bunch, so I'm anxious to see where Mazda goes with its replacement.
2. Passat- I've only briefly driven the current Passat, but I've riden in a friend's on multiple occassions. I think VW dropped the ball on exterior styling in the Passat's current run, but it still manages to look and feel a cut above in comparison with other midsizers. Attention to detail is more impressive in the Passat than in many other midsizers I've experienced.
3. Legacy- The Legacy appeals to me for many of the same reasons the Mazda does.
4. Aura/Fusion
6. Accord- I've driven the current Accord V-6 on several occassions and was unimpressed each time. The interior is a strong point, but the driving experience is overrated in my experience.
7. G6- The G6's exterior styling has always appealed to me. Interior quality/design is a low point, as is the lackluster driving experience. The G6 has always struck me as an enormous leap from where it's predecessor left off, but as is often the case with GM, that simply isn't enough. I'm anxious to see what Pontiac has in store for the G6's successor.
8. Malibu- more of an appliance than even the Camry, both inside and out.
9. Impala
10. LaCrosse
11. Grand Prix- I've said enough about the W-bodies in previous posts. Simply put, I drove a Grand Prix rental for roughly a week and was thoroughly unimpressed.
Omitted for lack of experience:
Camry
Galant
Sonata
Optima