5th Cell had a great idea when they created an engine where they allow the players to create their own solutions. It's a shame they didn't tap into the same creativity they wished to inspire in players with their own level design. Scribblenauts could have been so much more than a boatload of challenge levels which are often solved by a handful of overpowered items.
Should a sequel arise it would do well to have some sort of an adventure campaign with unique challenges that require gamers to think outside the box, much like this game should have. As it stands now, Scribblenauts is nothing more than a toy box with limitless potential in a house designed by an uninspired architect.