All in all, it really depends what kind of gamer you are. I don't see where the "Zelda gets better and better with every game" came from. The WW for example. It wasn't exactly the best Zelda game to roll around, specially with those graphics. To me it was a step down from OoT and MM, which I rarely liked in the first place.
StarFox isn't much different. I loved 64, but Adventures and Assault, not so good. Though, I play them a hell of a lot more then I would the Zelda games, cause to me their a lot more fun. Nothing like shooting your friend out of the sky with a Landmaster Tank... XD
Anywho, both series have their ups and downs, like everything else in this world. I've never found the Zelda games entertaining, and Star Fox, along with Zelda games get repetitive :P