I think mdb has the correct answer. The real distinction is between companies that practice excellent design, and those who simply buy generic gear from generic OEM suppliers.
It's too simplistic to talk about a product being "made" overseas. Even products made in the US typically have significant component manufacturing coming from all over the world. Atomic, who I'm working with now, makes their regulators and the Cobalt computer in the US- but individual components come from many countries. Their fins and masks and snorkels are molded overseas, but to their designs, under close supervision and with fanatic attention to design detail. That's very different from just ordering a container of McMasks from a generic molder and slapping your logo on them. And distinctions are not hard and fast- Oceanic is both a manufacturer in their own right and an OEM supplier to other brands. Some of the trendy-techy brands that are often mentioned have essentially no manufacturing ability, and contract everything- clearly their following is due to good design, not place of manufacture.
In regulators (as far as I know) Sherwood, being a huge valve manufacturer, did almost everything in house- apart from mining the metals, that is- and they don't usually make "best" lists. In the past I've personally worked with Poseidon, DUI, Viking, Zeagle, and a number of other equipment manufacturers, all of whom do or did their own manufacturing.
It's important to realize that one size does not fit all, there are different diving environments, and any best list is going to mostly reflect individual preferences.