NVIDIA (NASDAQ: NVDA) stock has returned a whopping 1,730% over the five-year period through Sept. 17 -- nearly 20 times the S&P 500's 88.7% return!The graphics processing unit (GPU) specialist's return also sprints by those of its main competitors, including Advanced Micro Devices (NASDAQ: AMD), or AMD, which has returned 749%; and Intel (NASDAQ: INTC) and Qualcomm (NASDAQ: QCOM), which have returned 126% and 26.5%, respectively, over this period. With this superb long-term performance, many investors are likely wondering if it's too late to buy NVIDIA stock.