A very good advice is just placing much less importance and effort into ideas, as "a good idea" is most often worthless - as far as gamedev is concerned. This is slowly but surely becoming a cliche sentence at this point but: Execution is everything. You can have the greatest idea of all time but unless it's executed well, it will fall apart.
However, a mundane, generic or "boring" idea can end up being brilliant if the execution is just right. Remember that Mario is a plumber that's trying to save a princess from being kidnapped by a turtle.