I've used GW, Vallejo, Reaper, Reaper Pro, Ral Partha, Floquil Model/Airbrush paints, Folkart/Creamcoat/etc and several others.
I like my Vallejo best, followed by the Floquil and Reaper.
The craft store paints I use for terrain/big projects, as their lack of density in pigments and inconsistent medium can often require multiple passes to get a coat on a mini or sometimes just plain screw it up (chalky texture, inconsistent drying, etc). Plus, they are inconsistent not only between brands, but between colors within the same brand and even lots of the same brand/color; I've used a certain grey with Folkart, and then got another pot of it much later and it went on much different. But for cheap paint for basic work, or for bigger projects where you can afford to slop it on, they can work fine (but still inconsistent).
The floquil (and other brands) of paints used by military scale modellers tend to be very fluid and have good pigment density, and are perfect for brushing on vehicles/models/etc if you dont want to use an airbrush. They do not drybrush well, however, because of their 'runniness'.
Vallejo gives me the best of all worlds; great pigment density with super-tiny particles, a good flowing medium that can easily be thinned or thickened without compromising the paint's characteristics too much, and those super handy dropper bottles. I've used a few Reaper Pro's recently and I'm liking them almost as well.