The path to entry-luxury success is littered with Infiniti G20s, BMW 318s and Mercedes C230 hatchbacks. But automakers persist. Mercedes will bring the next A-Class here, and Audi has plans for a revamped A3. You can hardly blame GM for bringing us a Buick version of the Cruze, especially given the Buick's differences. Holes in the automotive landscape reveal untapped opportunities — or simply no demand. Time will tell what Buick found.