I personally never spent time with this. I have a pavlovian reaction to my ringtone, where I'll get a jolt of stress whenever someone calls as I always assume it'll be some big work related problem. Last thing I'd want is knowing by the ringtone who it is that needs me.
On the other hand, my latest cellphone uses some algorithm to create unique variations of the same ringtone for each caller, which I do use. The variations are pretty subtle and it seems to help reduce incoming call related stress as it's always slightly different. I'm also just a sucker for technology like this.
My cellphone is an old showroom model, an LG G6, which at one time used to be a flagship phone I've gathered. I only bought it because it was dirt cheap, but I am very impressed by some of the nifty technology LG is offering, to the point where I'd actively seek out an LG phone for my next replacement.
My mom's ringtone is Metropolis being destroyed by the World Engine in Man of Steel.
I have no time for anything in my life except things that don't matter (work), but I just spen 45 minutes (while doing something else) curating custom ring tones for people that call me regularly.
As an incurable audio editing person this makes sense, but I wondered, how many of you waste, I mean invest, time in settign up custom ringtones for people who call you?