Good question how do you define worship I think it's to do with content and quality expressed in the way of love of God and fellow man. Also good worship involves saying thank you God for all thats good .
I would say that if it's good worship in a building like a hall associated with main stream christianity for instance take a look at the prayers , hymns or songs, sermons and even the architecture of a magnificant building with it's religious symbols .
However a simple mud hut in Africa can be a place of worship so it might boil down to true love as expressed in the content , practice and method . On the other hand kneeling down in the great outdoors and praying would be classed as worship.
So to sum up perhaps it's to do with content and to me the JWs meetings are more like a product sales get together repeating over and over why they have the best product when in truth they have a faulty product with very little true love for their fellow man.