Ultimate Good

Aristotle says that the best way to live life is through happiness or the ultimate good.  He says that it should be our end.  As good as this sounds I do not agree with him.  Yes it would be great to have the ultimate good but shouldn't it be up to the person to decided?  Everyone is different and have different cultures.  Sometimes people may not believe in the ultimate good because it conflicts with their culture.  Aristotle does not take other cultures into consideration.