I've always followed the practice of keeping a few sunfish or perch every now
and then, to control the population a bit. These days I have a simple rule of
thumb: If the fish is hooked in the lip or jaw, it gets released. If its
hooked in the gills and bleeding, it gets kept. (this is mostly for trout, as
they tend to go belly up if hooked in the gils and released.)
As far as eating quality, yellow perch and chain pickerel are tops for me,
with crappie, rock bass, bluegil, pumkinseed sunfish also being good. But I
think the body of water the fish comes out of can greatly affect the table
quality. The best tasteing fish I have ever eaten have come from clean, clear
mountain lakes or streams. Fish from murky, algae-infested, or other wise
discolored waters vary from barely OK to downright aweful.

-Zimmy