I'll agree that Naruto was good early on, but I'll disagree on the episodes. I'd say 1-60ish was pretty solid, but after that it really went downhill, though it did experience a resurgence when they chased after Sasuke-in-a-barrel. Plus, has anybody else noticed how anytime they have a gargantuan hour-long special episode, that particular episode always blows completely. Gaara v. Sasuke? Sasuke wasn't even hurt. 3 Sannin fight? Lamest fight ever. And what happened to "one full blow from Tsunade will kill me?" I seem to recall there were like 5 of those, and at least one super-full blow.
Okay, gotta stop before the vitriol overcomes me.
But yeah, there really aren't too many "bad" gateway anime out there. Sure, they might not be the cream of the crop (though many do flirt with craptascity), but they serve the important role of birthing future full-grown otaku. Even Robotech is impressive while a total bastardization of three different series (so wait... you combined three unrelated shows... and the plot works...). Heck, I won't hesitate to admit I like the first season of Pokemon reasonably well, and I used to love Monster Rancher. The closest thing in my mind to a "bad" gateway series would be Bleach if only because its completely uninspired. It lacks the wit and charm that make several of the other Shounen Jump series enjoyable (Yu Yu Hakusho, Flame of Recca), nor does it have the originality of Dragonball/DBZ. And yes, I do feel weird inside admitting DBZ was reasonably original for its time.