I confess that I am not quite sure about the usefulness of this question, but after getting to know of a few textbooks in German and Portuguese, I've certainly gotten curious:
Do you know of textbooks on analysis (anything from real analysis of several variables, through complex analysis, up to measure theory and functional analysis) in any language other than English or Russian? I suggest this exclusion because English books are definitely the most numerous and well known over here, while Russian books are already famous, as demonstrated by the amounts of requests for specifically Russian/Soviet textbooks in math.se.
I figure that at the very least this might inspire some people to peek books written in languages that they are learning. Who knows, perhaps there are some hidden gems.
There are lots of French ones. In functional analysis, Riesz & Nagy "Leçons d'Analyse Fonctionelle" comes to mind.