I'm not fan of the Nissan interior styling but they do make good cars.
Of the Chevy and Toyota I think it's a real toss up. For years Toyota has led the industry in reliability ratings and customer loyalty. But in recent years Toyota has slipped off that pedestal because they ignored their core ideals in their pursuit of fast growth. They wanted to be #1 in the world and beat GM in sales, but their quality suffered in the rapid expansion. The Camry and the Tundra have suffered from several recalls and bad press about poor quality.
Chevy on the other hand is going in the opposite direction. For years they were looked at as the working class car, basic, no frills with no style but a decent car for a good price. SUVs and large pickups carried them through 2 decades of sales. The gas crisis made them refocus on the family sedan and GM (and Chevy in particular) has improved their style, their reliability and their image over the past few years to become one of the cars to beat at the top of the midsized sedan market.
Is an Impala as good as a Camry? Maybe not, but it's a lot closer then most people would think so you have to give it an honest look. Get out and drive them both, see which car feels better on the road, who offers the most options and features you'd use. Which one looks better and has the better fit and finish. Who is offering the best deal and providing the best customer experience? Who is offering the best warranty and service after the sale? That's who should earn your business.