In my opinion, the most sensible way to handle genres as they relate to the artist pages is to gather them from the release groups they are on rather than having people add them to the artist themselves.

It can be misleading when you an add genres to the artist themselves. Some artists with very diverse discographies may only have their most popular work represented among their genres (e.g. Jim O'Rourke is best known for his folk and pop albums, but he has dozens of ambient, EAI, and drone albums). The opposite problem may occur where an artist is mostly consistent but has some releases that are outliers, so somebody voting to represent both their most common work and their less common work will end up giving both the same weighting, which would be an inaccurate representation of the artist.

I think the best way to handle the genres listed on artist page would be to gather up the genre votes across their release groups and list them on the artist's page. For example, Marty Robbins' cowboy/country music would still have the most representation on his page, but his Hawaiian pop would also be there (but with less votes).