In a quest to prevent players from reselling their used games, increasing replayability is often suggested as a possible solution.
But replayability is experienced by each player differently. In order to understand the different replayability approaches we must look at the different type of players and how they play games:
1. Challenge Players: these players consider the game as a challenge they need to overcome. So any form of reward that measures their success forms an incentive to replay the game in order to improve their score. Achievements and Trophies which can't be obtained through the first playthrough are a good method to encourage replaying the game.
Any form of high score (laptimes, points etc) also encourage replay, especially with online leaderboards. The great advantage of these methods is that the incentive for replaying comes from the player himself, who will always try to beat his latest score.
2. Collection players: these are the kind of players who go after each possible achievement/trophy, who will try to unlock extra costumes, game art etc when these are available in the game. Off course these achievements should not be obtainable in a single playthrough. Unlike challenge players, the incentive for replay must be included in the design from the beginning.
3. Story players: These players enjoy a game because of its story and are the hardest to convince of a second playthrough, since they already have seen the story and are likely not interested in replaying the game.
There is a solution to extend gameplay for these group by including second characters whose storyline is not entirly visible during the first playthrough with the main character (like the two brothers in Call Of Juarez).
In general, including achievements/trophies is an easy form to entice challenge players and collection players for a replay, yet story players are harder to convince and unless the stories are specially designed for replay, they won't likely bother to replay a game.