There hasn't been a 'bad' tales game in almost a decade.
Mediocre? Sure. But it shares the JRPG crown with Persona right now.
Not really. There are abundance of Tales games but they didn't exactly dominate the scene. Zestiria is a prime example.
They just happened to be benefactors because the competitions that used to kick their ass (Suikoden, Breath Of Fire, Wild Arms, etc.) have disappeared into oblivion. They are like the Klitchskos of JRPGs.