wow, Man that's a lot of responses. I don't play Xbox, but I do play a lot of iOS games and they added achievements a while ago. I don't know why, but i always like the secret achievements where the achievement works as a hint. in Kingdom rush for example there was an achievement for finding the yeti on one level there is a Yeti frozen in ice. I couldn't figure out how to "Find the yeti" until I cast fireball on the ice, it shattered and I was now able to hire the yeti as a hero. I think doing vague achievements as a sort of hint for strange stuff could be fun. like maybe you have an achievement called "Atlantis" and then I notice I find a scroll of water breathing. well maybe I go to this lake and try out my scroll and walk into the water and I find a giant city to explore. Now this could all be accomplished in a million other ways in game, but its still good to think about stuff like this.
and now for a gripe. I recently released a game and I was shocked how many people wanted achievements. The game allows you to play and get a better rank, diamond being the best. People wanted an achievement saying they got diamond even though I gave them a large diamond idol in game. It seems achievements are slowly moving towards the realm of the skinner box. and people love to see that thing ppop up at the top and drive their player score up.
has any one played Bastion? it has something called idols, or something. I always thought they would be a good addition to a RL. They are similar to the skulls in Halo. you are given a large amount and you can turn any of them on or off, before you enter a level. you can have stuff like more enemies, stronger enemies, no magic, all enemies poison, enemies give double XP. letting the player mix and match these could be really cool.