Triforce and
tunepunk your 100% right on the mark!! His game actually is doing very well with ADs. The reason is because the type of game he made is not just a pickup and play but goals oriented game with many missions. That keeps users coming back for more, including myself.
You need to give players a reason they should come back to the game. Thats why instead of jumping in to make a game you have to think about what can your game feature to keep users coming back. Also means you have to learn the toughest parts of Construct2 which is the various save features. If you game has stuff like in game shop to upgrade your hero , missions screen with various missions, or in game achivements so people can unlock various achievements without internet connects. Basically you need to give the player alternate goals to complete in the game, that gets players hooked to keep playing and unlocking stuff within the game.
For example right now I been working on a game and added a missions section. In this section you have various missions to complete in the game to unlock the checkmarks. Stuff like how many enemies you defeated, total powerups collected in game, highscore etc. This will keep the players coming back because players always have the need to unlock everything in the game.
I know programming all types of various save features can be mind numbing. I found it tedious to do the missions screen but its a very important feature to keep players hooked. In the past I was lazy about it but I realized all these things add up to a great product.