In the market for graphics cards, NVIDIA and AMD (which owns the Radeon brand) are both well-known and respected brands that offer high-quality products. It is difficult to say definitively which is "top of the line," as the performance of a graphics card depends on a variety of factors, including the specific model and its capabilities, the system it is installed in, and the specific graphics-intensive tasks it will be used for.
Generally speaking, NVIDIA is known for its GeForce line of graphics cards, which are used in a wide range of applications, including gaming, content creation, and machine learning. AMD's Radeon graphics cards are also widely used and are known for their performance in gaming and other graphics-intensive tasks.
Ultimately, the best graphics card for you will depend on your specific needs and budget. It is a good idea to do some research and compare the features and performance of different models before making a decision. It is also a good idea to consult with a computer hardware specialist or a salesperson at a computer hardware store for more guidance.