Red Bull Games Australia has explored just why it's important Nintendo looks at adopting and Achievements/Trophies-like system...
Here's an excerpt:
"Nintendo makes games about bragging rights. It might be incidental, but their basic design of games is essentially a service to completionism. The bare minimum still exists for non-completionists, because that’s how Nintendo goes about it, but their in-house games are designed for gamers to explore every little thing; to find new secrets and hidden goodies -- to collect ‘em all, if you will.
120 stars in Super Mario 64. Skulltulas in The Legend of Zelda: Ocarina of Time. Routes and Medals in Lylat Wars (or Star Fox 64 for non-Aussies). Chozo Artifacts and 100% scan completion in Metroid Prime. Racing ghosts in Mario Kart(s). Your damn Pokemon collection, from common to rare, to legendary – Nintendo’s game-design philosophy is about 1-Up-manship (heh). But beyond personal accounts, or playgrounds and watercoolers, there’s no tangible evidence of any level of completion for players in a digital social sense..."