I had the 10/22 carbine (base model) a mossberg and a rem 597 side by side at one time
I will say that the mossberg was more accurate out of the box. sub inch groups when I found the ammo it liked best.
the composite stocked 597 was also a very nice gun, but felt "cheaper" compared to the other 2, having about the same accuracy as the 10/22 out of the box.
service wise - the 10/22 was the clear winner hands down. it feeds more brands of ammo, more reliably, with a more consistent level of accuracy than any other 22 I own besides my buckmark pistol (which is on even par)
If use and preference can be an indication of which is the best one, the 10/22 was the hands down winner (for me) there as well. I found I always grabbed it first.
Are the other 22 autoloaders available bad guns? certainly not, not by any means. But after thousands of rounds the 10/22 (for me) emerged as the most consistent and trouble free of the bunch. My friend now has the 597 (which he loves completely - to the point of constantly ragging me about my ruger) and my sister has the mossberg (which still excels at taking out gophers - and is entirely jam proof - as long as you feed it winchester super x hollow points)
Now - I did modify my 10/22 with a replacement (factory style taper, not a bull) barrel and a trigger job. and the walnut sporter stock (I'm a sucker for blued steel and wood - what can I say) After those modifications - it's a ragged hole 50 yard shooter and a sub inch grouper at 75 yds off a rest using several brands of commonly available bulk pack ammo.
Bottom line - Is it worth the premium over the other brands? IMO Every penny.
I think it's the most commonly sold 22 out there IIRC, but then again - it also has a fantastic marketing campaign too, and there's seemingly one in every gun store you walk into, so it's availability may have something to do with that.