Like creating a "fresh" character in ME2, starting a non-imported character in ME3 has pre-defined decisions for the previous games already made for you. However, is there any other way to get around this? Is there any DLC available that's similar to the Genesis comic for ME2 on the PS3 that I can use to change the back story/decisions of my character?
There is no 'official' way to do this. The game gives you the ability to make a few key choices at character creation (Specifically, you can name the Virmire survivor, or claim that you've experienced "numerous" losses, which results in a large number of otherwise surviving characters dying.)
As an unofficial option, you can grab a save file that fits your criteria from MassEffect2Saves, and/or use a saved game editor before importing.