Artificial intelligence (AI) is sweeping across every industry. Researcher IDC forecasts that AI will contribute a total of nearly $20 trillion to the global economy over the next five years. By 2045, AI could drive enormous returns for investors who invest in the right stocks.Here are two stocks that could deliver tremendous returns over the next 20 years. 1. NvidiaNvidia's (NVDA 1.26%) dominance in the market for graphics processing units (GPU) -- vital hardware for handling AI workloads -- has placed it ...