However, here's what we can consider:
* Yu-Gi-Oh! (original) has been around longer and is considered a classic, with a large, dedicated fanbase. It also spawned a very popular trading card game which significantly boosted its popularity.
* Yu-Gi-Oh! GX is a spin-off series with its own loyal following, but it might not have the same widespread recognition as the original.
* Streaming and digital availability have made both series accessible to a wider audience, potentially skewing viewership numbers.
Therefore, it's likely that Yu-Gi-Oh! (original) has a larger overall viewership due to its longevity, popularity, and the impact of the trading card game.
However, Yu-Gi-Oh! GX is still highly regarded and enjoyed by many fans. It's important to remember that "most watched" can be interpreted differently based on various factors, and there isn't a clear-cut answer.