Use existing libraries whenever it makes sense.
I'm guessing that you don't really think that things like iTorque 2D are a good idea.. like cheating? And in the long run, not such a good idea as you're dependant on crutches that don't allow for much creative programming.. would that be a correct way of seeing it?
A game like Tiny Wings is a bad fit for iTorque2D and other engines.
The game engine is good for complex games. It has some overhead, but a good engine can reduce a team's efforts by several work-months or even work-years; spending a few weeks of effort instead of years of effort is a good trade.
Tiny Wings and similar games are essentially a sine wave ground height functions, and two variables for a sprite's height and velocity. It is a very simple game. Most experienced programmers could write a clone of the game in a week or less.
The overhead of using the engine far outweighs the effort of creating that type of game from scratch.