There were several others...
Access (Tex Murphy games)
Detalion (Reah, the Schizm games, Sentinel)
Kheops Studio (Return to Mysterious Island 1 and 2, Echo: Secret of the Lost Cavern, Safecracker 2006, Nostradamus, Secrets of Da Vinci, and
***more***.
Southpeak (Temujin, Dark Side of the Moon, and the 20,000 Leagues Under the Sea on DVD game that never got past being an ad on a poster in Dark Side of the Moon and a demo.)
Also, the dates they give for Sierra are 1979-2008, even though it wasn't the same studio for all that time -- and the Vivendi incarnation was certainly not "beloved."