Generative AI (GenAI) may offer a transformative potential for marketing, but realizing this requires a strategic, organization-wide approach. This white paper, based on a comprehensive study conducted by the MMA/MarCaps partnership (n=521) and interviews with leading CMOs, explores the challenges and opportunities inherent in GenAI adoption. We introduce a strategic framework, the "Need-Case Map," to guide marketers in prioritizing investments, aligning initiatives with business objectives, and maximizing impact. Our research reveals key differentiators of leading firms, emphasizing the critical role of a need-case-driven approach, robust organizational capabilities, and a structured roadmap for navigating GenAI deployment.