If there's one feature of Spore that should be adapted to many other games, it's the creature history timeline. A visual history with snapshots of memorable and personal moments in a player's game experience offers far more than a simple achievements system.
A cornerstone of good storytelling is reflection -- showing how past events are relevant to the present. Providing the player with tools for reflecting on their game experiences encourages them to view those experiences as parts of one story (his or her own), rather than random and forgettable events.
Seen as part of one's story, an event takes on personal relevance. The emotional connection is deepened, and the game becomes more important to the player.