First, being the most used does NOT automatically anything the most versatile.
Second, you guys are debating versatility and I suspect (I didn't read the whole thread) that you have not defined the term "versatility".
I think people here on TB fall into 2 camps on the definition of versatility. For some, versatility means that a bass can produce a wide variety of tones. By that definition, the G&L L-2500 with single coil mod, and the EBMM Bongo and Big Al are probably the most versatile basses made.
For others, when they talk about versatility, they mean that a bass sounds good when used in a wide variety of genres. By this measure, the "one trick pony" good old Precision bass may be the most versatile bass made.
So, before you debate further, perhaps you should clarify the actual definition of what you're debating over.
For my money, the Precision and its descendants and the MM StingRay are tied for "most versatile", because they virtually always sound good in a mix, no matter what kind of music it is. And the MM Sterling trumps them bit a very slight margin because it has the StingRay sound in parallel mode but also has single coil and series options which broaden its ability to sound good in any genre.
For my money, there is NO genre of music where you can say a Jazz sounds good and you can't make a MM Sterling also sound just as good. But, to me, there are times when a Sterling sounds good and you just can't make a Jazz sound as good in the same setting. ALMOST, but not quite.
But that's just me.
I can understand where you are coming from also, but even what you are saying is highly subjective. For example, imagine taking all those old classic recordings take with a P bass and try replacing them with a Ray, which you also said was tied for being the most versatile. It's hard to imagine any of the thousands of Motown hits being recorded with a Stingray. I'm sure some of them would sound great. I'm also sure they'd be very different, and for a number of people at least, not for the better.
Take a Jazz bass though, and you could pretty well pull off all those classic recordings by favoring the neck pickup heavily. Take any song recorded by a Stingray, and you could get in the ball park on a jazz by favoring the rear pickup. Exact in either case? No, but of course much closer to both than the other two could do for the other.
And then the Jazz has it's own thing entirely when blending the single coils.
You are right. Versatility can mean many things.
Still, as I said earlier, if you are going to record in a studio or do a session for someone, you better show up with a P and J bass at a bare minimum every time. Chances are than you'll always walk away successful if you can play and meet the demands of the tune. Show up with just a Stingray or even the Sterling? I doubt that would work out very well for very long.
The J and P basses are in high demand because of the way they sound, and the way that producers can get a tone they want out of them time and time again. That makes them versatile by their very nature, even if an individual player prefers something else entirely.
The latter is what I've been arguing here. If someone prefers something else and wants to play that, and even think it's better/more versatile, or whatever else, then they are certainly entitled to that and their opinion is valid. I just wouldn't expect too many other people to feel that way about it. I've gotten great compliments from other bass players when playing all kinds of basses, including MM, G&L, and some modern basses as well. I've even had sound guys and producers tell me they sounded good. But bring a J or P bass, and the engineers and the rest of the band always love you. They just work every time. IME/YMMV