I don’t think it’s a big deal where you start. The latest iteration of Riven will likely be the most accessible and that’s probably what matters most if you’re just starting out.

Much of the appeal (for me at least) is that the storyline is a Tolkien-like epic story spanning thousands of years. Myst takes place before Riven, and if you wanted to consume it in chronological order you would start by reading the books (which are surprisingly good). But it’s fine to go back and “fill in the blanks” if you play in a different order.