Erik Torenberg's Village Global [1] was started fairly recently and is already extremely highly regarded in the start-up community. Much more so than Techstars or any other non-YC accelerator in my impression.
500 Startups and AngelPad also seem fairly well-known. I'd love to hear from someone more involved in the VC community about how those two accelerators are generally regarded.
If other accelerators compete with YC, entrepreneurs may choose to do business with an accelerator that selects smaller classes.