In the real world, a "good" bottle of wine is one that you enjoy.

Gallo is a family-owned winery and has pride in family the name, unlike the two corporate entities that it competes with as members of the Big Three (my term) vintners in the US who (probably) produce 80% (by volume) of all US wine.

Gallo has 16,000 acres of grapes they own, most in or near the Central Valley of California. They have thousands more acres under contract,

Merlot is produced in quantity, often to be blended with the varieties.

Because they have huge amounts of money, Gallo can buy small wineries in better regions such as Sonoma County. They sometimes market mass-produced Central Valley wine under the recently-puchased name, sometimes they keep the original outfit reasonably intact, and once in a while they attempt to put out a superior product under their own name.

I suspect that Gallo's Sonoma County Merlot and other varietals from that region are quite good. Not really cheap, though.