Subaru, Honda, Nissan, Toyota, Mazda. List them in order, from most reliable to least?

Generally speaking.

1-Toyota
2-Nissan
3-Honda
4-Subaru
5-Mazda

Toyota
Honda
Nissan
Subaru
Mazda

Depends on the model.
All of these manufacturers have at least a couple models that have average reliability, or better.
Most to least - Toyota, Mazda, Honda, Subaru, Nissan

Suggest you have a look at JD Power's studies: http://autos.jdpower.com/

It depends on who owned it before and how well it was taken care of.