You are asking the right way to say things we typically would not say.
Who is your favorite footballer and cricketer? The form of this question suggests they are the same person, and it's conceivable one person might be good at both, though of course we doubt it. In other cases, they certainly could be the same person: Who is your favorite singer and songwriter? Best to make it clear and separate the two: Who is your favorite footballer? Your favorite cricketer?
Who are your favorite footballer and cricketer? I don't like this form, as the verb and noun(s) do not agree in number. In reality you are asking two questions: Who are your favorite footballer? Who are your favorite cricketer? Wrong.
We could allow that one might have more than one single favorite in each category: Who are your favorite footballers and cricketers? I see nothing wrong with that, and one could certainly respond with single choices: 'My favorite footballer is...' Better though, if we change your sentence just a bit: Who are your favorite football and cricket players? Now the noun and verb agree in number.
