TW: Atilla would probably be superior to Rome 2 if you consider that Rome 2 was some type of Beta and brainstorming ship for the Creative Assembly staff, they have tried to reduce some concepts to make it more accesible to more gamers but it didn´t quite hit the mark. In the end they have fixed a lot of main problems that surrounded the game like the civil wars and sieges and it´s really playable in it´s current state and will make you play a lot of hours. The thing is that Atilla is aimed for the tradicional costumer of the TW franchise by adding family trees (wich was/is very aclaimed), making more dynamic fights, improving the campaing map and giving that feeling that gave Rome 1 barabariam invasion.
I´ll personally buy it on release like all total war games, will give all the feedback I can give and I´ll start modding it for the community. Wich is what I love, and maybe (MAYBE!) some people make a third age of TW: Atilla becouse it has a lot of potencial if they release all the things they said they are going to put in this "standalone expansion"