Know why I love Batman: Arkham Asylum? Well many reasons, it is truly a fantastic game, but the real reason is how it handles collectibles.
Many games have them, scraps of paper that tell a story, audio clips relating a nightmare, things like that. Arkham Asylum has patient recordings and an audio diary split into many parts on Arkham's history. All of the material is amazing and what they did that was unique was never present them out of order.
Each main villain has 5 patient logs where they talk to therapists, even if you find one, let's say the third you found for Joker, and in fact it is the fourth one you COULD have found, it is listed as the third. Basically they don't (unlike every other game) dictate that a recording is number X. Every recording is the next one in sequence for that person no matter where you found it.
This is a smart move that is actually quite simple really, but no one else has really done it before...kudos Rocksteady for thinking outside the box.