5. Angry Birds Space
Scoff all you want, but there's a reason Angry Birds is as popular as it is. The bird-flinging simulation is immediately accessible, with controls that anyone, gamer or not, can grasp in a few seconds. And that's not because they're overly simplified or anything - it's thanks to the design, which is intrinsically basic. You have a slingshot, it throws different types of birds, and you need to launch the birds at structures to destroy pigs. The sequel, Angry Birds Space, takes that idea a few steps further, adding in the concept of planetary pull and zero gravity - which, as you could expect, has large implications in game based entirely around... well, gravity.
The inclusion of planets and space allowed the developer to create varied puzzles that had us completely hooked, trying time and time again to find the perfect angle to launch our birds in order to take down the pigs. It's not the highest of all concepts, but it's fun, simple, and can make a six-hour flight go by in the blink of an eye - or the toss of a bird, as it were.