What makes a toy hot? Is it hot because it's on TV every 20 minutes in front of your kids or because all of their friends have it so they absolutely must have one too? Or is it hot because it's based on a character they truly love, a passion that they have or their own unique play style, even if they haven't asked for it yet?
Children who play with piles of Legos, inventing and building as they wish, exhibit far more long-term creativity than children who build things from Lego kits. Rearranging Legos from a messy pile is a better learning experience than working from a kit with directions (unless you're in a hurry and hope to use the finished Lego product as a household appliance).