Between GE, Philips, OSRAM, Sylvania, and other big brands, which one, for you, made the best possible HPS lamps?
Best in terms of luminous efficacy, lumen output, build quality, durability...

I know GE is the original creator of the HPS lamp.

I'd go with Osram and Cromptom, specially the latter cause the one lamp I do have is a much more orange-y color than a regular HPS.

Pre-1990s GE Lucaloxes.

Post-Westinghouse buyout Philips lamps with either a BT or ED envelope, through the late 1990s. They refined the arc tube design without cutting too many corners.

@DidiusMalloricus - Your question isn't as simple as one would assume...it all depends on the era. They all have there good and not so good eras...here's a rundown:
General Electric Lucalox from 1970, to 1995 is very good quality. Near the late 90's quality started to slip...especially when they started importing them from their Hungarian (Tungsram) factory. (Exception: GE's line of DX HPS lamps.)
Sylvania Lumalux from 1970, to around 1992, was excellent top notch quality. After the sale to Osram, quality started to slide...almost imperceptibly until is was pretty obvious around 2005. At some point, production was moved from Manchester to Mexico, then China...total junk compared to what came before.
Philips Ceramalux from 1984, ('84 to '88 still the best years) to around 1996 were well made...durable monolithic arc-tubes, with good welds. Sometime after '96, they cheapened their product significantly with sloppy welds that could easily break simply by tapping the lamp against your hand (first hand experience). Exception to this was their Comfort line which were well made up to the closing of the Bath plant.
Westinghouse Ceramalux from 1970 to 1981 was well constructed and with a beautiful appearance (Corstar) that other makers didn't bother with, even though GTE-Sylvania came close. Bad years for reliability: 1982 to 1984, when Philips updated the design with their superior monolithic arc-tube.