That’s a great question, but it really depends on who you ask.
Remember that each certification has its own prerequisites and process. A certification that requires a college degree doesn’t necessarily mean that it is better than one that doesn’t.
If you are looking to get employment at a club, then call the club and ask which certifications they prefer. I did that and found that, in my area, ACE was preferred. In fact, as I am starting a new job as a group fitness instructor, my specialty format combined with my ACE personal trainer certification helped me land the job, despite not having a specific group fitness instructor certification (which I’m working on right now).
If you plan on working for yourself, find out which are certified by NCCA and see which fit your budget, education level, and goals. That could be ACSM, AFAA, ISSM, etc.
See what works for you and what your career goals are. Like it says in the “7 Habits of Highly Effective People:” begin with the end in mind.