FreeCell is becoming increasingly popular because, unlike standard Solitaire, it is purely a game of skill. With perfect play, the player can win every game of FreeCell. At the start of the game, all the cards are placed face up, so it is theoretically possible for a player to calculate the solution from the starting position without moving even a single card.
On the other hand, the game is hard enough that there are probably few people who can actually do that in their head.