If Poker is played for money, then it is gambling which is prohibited. If Poker is not played for money, it is still prohibited according to a number of scholars, because it is akin to dice in its dependence on conjecture and guesswork, and playing with dice is prohibited.

In Islam, it is not permissible to play backgammon because it involves the use of dice which are haram and emphatically forbidden. For more, see the detailed answer.