They actually mix up the Tales games a lot. They release twice as many as they should, but each one is pretty different. They'll go back and forth between pure 2D and 3D, mix up the battle systems a good deal, and change character designers and art styles. Maybe not as sharp of a break from game to game as Final Fantasy, but still.
I don't know if it makes it better or worse that only half of them come here. But like... Symphonia, Legendia, and Rebirth you'd never confuse for an instant, and they were consecutive releases in Japan.
I think the problem is that the more you oversaturate, the more the need for change is exaggerated. If Tales games came out every 3 years instead of twice a year, the amount of change between titles would be more than enough, but when there's so many of them so often you're like "Shit, make one set on the Moon or something. I just played one of these 6 months ago."

