If you think you have a superior product then don't 'cut your losses' :)

Change the name of your app. From what I can tell, the app name in question is very generic since it

a) describes the game itself

b) was taken up by a competitor in the same field

Give it a more unique name.

Canabalt sounds much nicer than 'iRunner'

Frankly, if I were looking for a blackjack game, I would be more likely to click on one called 'DoubleDown' than one called 'BlackJack' (though admittedly that's just me)

Keep your current domain name the same and use it or additionally secure another domain for your app.

Names are overrated. If you don't believe me, look at the names of some of the top sellers