Except for Motta the Hutt of course!
The mind trick is only supposed to work on the weak willed. I wouldn't expect a crime lord like Jabba to be weak willed.
Watto's species might be immume to the mind trick because thier brains are very alien. Hutts may be alien enough to give them some resistance, but not enough for full immunity.
I'd rather go with the "weakminded" theory( Wow, look mum, I'm a nerd ) Watto might have been a screwup in the technical department but he might have had some good bargainin skills and strong will to the point that simple "force persuasion" didn't work for him. If a whole race is force resistant wouldn't the jedi council know about it since it is an important deal for them to know?
As Shdy put it, this is yet more discontinuity in the SW universe. Isn't the current EU standing is that Hutts are resistant, whilst Toydarians are immune, or somesuch?