is there really only one most versatile cheese? It seems to me it depends on whether you want to eat it "out of hand", use for sandwiches or cook with it.
I favor hard cheese with lots of flavor since these are good for "just eating" as well as cooking.
>An aged xtra-sharp cheddar (not artificially colored to make it yellow or - gasp! - orange)
>parmigiano-reggiano of course, tho I personally like pecorino-romano just as well and it is significantly less expensive
>smoked gouda (not really "hard" - has good melting properties and tastes great)
Sometimes I buy a triple-cream blue cheese from France (sorry, can't remember the name) which is marvelous on whole-grain bread, crackers or with apples (I love cheese with apples or apple pie). If I'm feeling really decadent, I'll have some sherry or port with this.
>fresh mozarella and fresh smoked mozarella - I adore this and we know it's great in cooking but in my house it always gets eaten as soon as it can be unwrapped and put on a plate (especially in summer with fresh tomato slices and an assortment of olives and pickled mushrooms and artichoke hearts)
>last but not least, I like that processed "port wine-cheddar cheese" stuff from the supermarket with crackers and/or apples