Tough, given all the great singles that have blessed the industry this year, but yeah, something like:
1)
Problem - Ariana Grande ft. Iggy Azalea

2)
Fancy - Iggy Azalea ft. Charli XCX

3)
Pretty Hurts - Beyoncé

4)
West Coast - Lana Del Rey

5)
Human - Christina Perri
*
Into The Blue by Kylie and
Sirens by Cher Lloyd would be the runner-ups for the fifth spot...