Tales series should definitely slow down, but I don't want Namco to retire the series. Just focus on quality over quantity :\
Metroid and Zelda would be my nominees. Both of these series used to be leaders in coming up with creative challenges and gameplay mechanics, and now they're pure formula. There have been far too many entries in both series lately and they all involve collecting the same power-ups (hookshot, Morph Ball, etc.) to solve the same puzzles over and over. Actually, if they came up with some major new direction (as Majora's Mask did), I'd be happy to see the games continue as I used to adore them, but right now they're just nothing but the same thing over and over.
I'm including Metroidvanias in with Metroid
Oh, and everything Megaman, but I haven't cared about Megaman in years, so that bothers me less. Whereas I used to love Zelda and Metroid, so it's frustrating to see the games so average these days.