Solution: (1) All possible results are obtained by tabular method, as shown in the following table:

As can be seen from the above table, there are *** 16 possible outcomes of the game, among which there are 5 outcomes in which the product of the numbers on two cards is greater than 20, so the probability of winning is P A =5/ 16.

(2) This game is unfair to both sides, because the probability of A winning is P A =5/ 16, and the probability of B winning is P B = 1 1? / 16 ,

5/ 16≠ 1 1/ 16

So the game is unfair to both sides.