In blackjack, the cards that are better for the player are the high cards, specifically the 10, J, Q, K, and A. This is because these cards increase the probability of getting a blackjack (an Ace and a 10-value card), which pays out at a higher rate.
While luck certainly does have a part to play in Blackjack, there is a lot of skill that goes into playing the game. How much skill or strategy you use depends on the time and effort you are willing to put into learning these skills. One such skill is card counting-not like by casinos but certainly not illegal.