I guess the main focus of the topic would then be HOW does the player interact with the things he has collected.
As Orymus3 mentioned, the game became dull because the formula of the game revolved around improving the same mechanic that gave you the resource.
Maybe the thing to do would be to gather resources which can be used in a wide variety of ways, such as wood. Wood has the potential to become furniture, fuel, buildings, weapons, tools; many things which could be useful in other ways.
I guess the challenge is to code a lot of interactivity with the things you create.