I agree with alldig and draqon on this one.
Products usually work better as plurals: costumes.com, domainnames.com, gifts.com, paintings.com, gadgets.com, pills.com, flowers.com, etc.
Exception would be where the singular form is commonly used to refer to the items in bulk: candy.com, coal.com, medicine.com, fabric.com, chocolate.com, artwork.com, software.com, beer.com, etc.
Words that describe fields are generally better as singular: business.com, mythology.com, sex.com, music.com, photography.com, military.com, etc.
The golden rule is, if you asked someone "What do you sell?" or "What are you looking for information on?", what form would they use?
Does that store sell game or games? You looking for information on game or games? Do you want to eat candy or candies? What do you need to study, philosophy or philosophies?