There is a truckload of apps that are iOS only. iA writer, paper, penultimate, infinity blade, just off the top of my head. Great quality apps abound, and usually their iPad versions make great use of the screen real estate, instead of just rescaling the interface.
Lots of others have started on iOS and were only released for Android much later (Flipboard, Angry Birds, Instagram).
Lots of others have started on iOS and were only released for Android much later (Flipboard, Angry Birds, Instagram).