There was a time when vBulletin was top dog, the best, and a clear winner. I would say at that time it was neck & neck between VB and IPB. vBulletin seemed to pull ahead because of the number of themes, plugins, etc (at the time). This went back and forth obviously and vB was not the top winner forever obviously.
Now so much time has passed, forum owners might have never even tried VB but in the early 2000s, it was a premium software that many wanted to use.
I have well over twenty vBulletin 3 and 4 licences sitting around doing nothing. My first forum ran on vBulletin 2 which I started in 2001. vBulletin 3 was by far the best version of the software but things went swiftly downhill when Internet Brands acquired Jelsoft. My early adoption of vBulletin 4 turned out to be a catastrophic nightmare and a lesson learned. Let others do all the testing first!
I'm currently using it for a forum right now! Though I wish I could have used it back in the day when it was more popular. I remember when all the gaming forums used vB or IPB, now most of them that are around still use Xenforo instead! Emuparadise was the forum I used most that was powered by vB3.
Can't remember which version I used before, but I used to admin a community that used vBulletin. Unfortunately, that community no longer exists, but I remember it being relatively easy to use as someone who isn't the most tech savvy person sometimes.
I liked it a lot from a member standpoint though. The first community I ever joined online many, many years ago was on vBulletin. That community isn't around anymore either, but I remember it fondly. Back then, a lot more communities were on vBulletin if they were using paid software, and I always enjoyed it.
I really miss vBulletin! It had such a homey feel to it and Xenforo has more of a professional feel. I wish that vb5 wasn't such a disappointment, or we would have upgraded to it for Christianity Haven.