Actually, I should probably clarify; when you say 'sparkles', do you mean things that sparkle all the time, or just sparkle once when you enter the area? Like for example, in Pokemon Ruby/Sapphire/Emerald, when first entering the Trick House, you see a little sparkle when you first enter, which reveals the Trick Master's hiding place; however, the sparkle stops appearing after the first three visits, forcing you to find him on your own on subsequent visits. Not sure if that system would be better or worse than just having permanent sparkles, actually. If the sparkle appears every time you enter a new area, there's nothing stopping the player from just leaving and then coming back in. If they only appear once then it becomes a potentially frustrating memory game if the player forgets. Perhaps it only worked with the Trick House because you were expected to visit it multiple times and it was just to get you used to looking for hidden things.