There are a lot of cities in
Central Europe that have "
legitimate" alternate names because of fairly large minority communities.
Prag/
Praha is a good example of this, as is
Danzig/
Gdansk. Many of these alternate names are in
German, in part because
Central Europe was for years dominated and then divided by
Prussia and
Austria --
kingdoms that were administered in
German.
In the case of Genf/Genève, the town itself is indeed in a French-speaking canton of Switzerland. But the country has four official languages, and the German-speakers of that country call it Genf and not Genève.