I have tried pre-made chicken broths, boullions, and soup bases, each claiming to have the best flavor. Of those I tried, College brand is one I like, though when you read the ingredients, it is not pure chicken broth, or stock. Better Than Boullion is the brand I currently use. It is a soup base and comes in chicken, turkey, ham, vegetable, and beef flavors. I find the chicken flavor is closest to home made of any I've tried. And no, I don't work for them. The beef flavor is very good too, but needs to be used carefully as it can quickly become overpowering. For beef flavoring, I prefer Washington's Deep Brown Sauce. It adds great flavor to beef gravies, sauces, and soups.
But by far, the best chicken flavor I have tasted is by boiling up a bunch of wings, and bones, to extract every bit of collagen, and nutrients from them, as well as flavor.
And if you brown the bones first, in the oven or under the broiler, it's even better.
And if you grill some bones along with boneless chicken, over charcoal of course, it's better still.
And if you raise your own free-range chickens, and let them eat bugs, worms, and native grains... Ahh, I'm just joking with the free range chickens. But it would be better.
Seeeeeeya; Chief Longwind of the North