Number of players: 2
Deal the cards equally between the two players. The players keep their cards face down.
The players turn over the top card from their pile at the same time. The player with the card with the highest value gets to keep both the cards. If the cards are the same face value then the cards remain where they are and the next card from each pile is turned over.
The winner is the person who collects all the cards. (Note: since this is a game of luck rather than skill it is good for younger players but you may want to impose a time limit rather than play until one person gets all the cards as it can take a long time)