That's how it is, all the top players that aren't Magnus are roughly the same level. The highest #2 streak in the last ten years was Aronian, who lasted 12 months. What's the highest #1 streak? Carlsen, with 70, with no end in sight to his streak.

We just don't have a defined #2 player. Sure, from your list it seems like Aronian is, but it just depends on the week -- Aronian could've easily not even qualified for the Candidates if he messed up one of the tiebreaker games at the World Cup. So who's number two? Caruana? So? Kramnik?

The situation we have now is very fickle, for example Segrey won the Candidates, and now he's not even in the top 10, some months later.

Basically (at least to me), Magnus's superiority is so well-defined that thinking of who's #2 to him is just a pointless exercise. There are the best players in the world, and then there is Magnus, and no one is challenging the space in the gap between the two. Sure, Shakh might have the #2 spot now, but it belongs to no one. Only the number one spot has a long-term resident.