The phrase "are so superb" is correct and usable in written English.
It can be used to express a strong positive opinion about something, emphasizing its excellence or quality.
Example: "The performances of the actors in the play are so superb that they left the audience in awe."
Alternatives: "are incredibly excellent" or "are truly outstanding."
Perhaps this is why the photographs of the Nenets in northern Siberia are so superb.
The meat salads are so superb, with their interplay of heat and chill, that you might happily construct a whole meal from them.
The cast regulars are so superb that even special guest stars such as Chris Addison can look slightly out of their depth.
His illustrations to the 1865 edition of Alice's Adventures in Wonderland, and later Through the Looking-Glass, are so superb, and so familiar, as to have become a shorthand for the books themselves.
Some of the grandiloquent compositions by the cinematographer, John Mathieson (who also shot Mr. Scott's "Gladiator," with its video-game-by-Bruegel lighting), are so superb that you want the movie to stop so you can take them in, as when Lecter is crossing a street in the rain and a white car shimmers in the light like a ghostly stallion.
I write about deflation and imagined that my companies are so superb that they wouldn't suffer.
In terms of handwork, the effect was so superb that it might have been a couture house.
Their timing was so superb and they had the ability to dissect a subject like a scalpel".
Generally, Osgood was so superb that the 14,378 in attendance were less reluctant to chant his name after big saves.
Their art is so superb in quality that it proves the existence of a higher mind, the capacity to create civilisation.
Fogerty's songwriting has been so superb for so many years that the album could have benefitted from a few more rarities: "It Came Out of the Sky," maybe, or "Effigy," or "Molina".
