Anyone can write a song. Heck, look at Rebecca Black's Friday.

Poetry on the other hand is on an entirely different level. Well written poetry captures imagery like nothing else; painting written art, each verse another stroke on the composed masterpiece. 
The imagery created by Owl City songs is unrivaled by anything I've heard by any other artist, making it musical poetry.

Adding the right music behind the poem is like sewing beautiful tapestries of word lace and artistically setting those masterpieces within a lyrical constraint. Owl City's signature "sound" (calming, uplifting synth) lends to the poetic nature of his lyrics.

The same goes for his floaty voice. They all don't point to song, but to poetry in its musical form.