No, The X's was not the most original show ever. No, it was not always consistent. No, it did not always know what it wanted to be. All those things said, this show still got WAY too much criticism for what it was back in 2005-2006 ( i . e . the time mainly considered the point where Nickelodeon went downhill), probably thanks in no small part to the fact that The Incredibles was still fresh in people's minds and everyone was on the "it's not original" bandwagon. I guarantee if The X's didn't coincide with the downfall of Nickelodeon, and it instead aired during the heyday, or heck, even today (when put next to even MORE horrible shows), it'd be viewed in a more favorable light.
While some parts of the show suffer from some awkward repetition, and some lapses in continuity, the humor is pretty spot on in most cases. The thing is, it's hard to find the middle ground for humor when it comes to shows like this, where the majority of it comes from dialogue. That's not something a lot of kids shows these days do, because many kids don't understand the dialogue or have the attention span to listen to it. That must have been obvious to many of the writers, and that's probably why they had to insert utterances like "Fartmonkeys", said by Glowface and Truman, into the show, to captivate the yougest viewers' attention. But really, when you look past that stuff, much of the dialogue is pretty damn good.
Voice acting is superb, my favorites being Mr. X, Mrs. X, Lorenzo Suave, and Home Base (all his subtle, "hmm, yes"s and bursts of outrage are awesome). And the art, this is something that people complained about back when this show was on, but in my opinion it's a strong point. Took me a while to realize it, but the art style is actually very unique without being jarring, and to me the simplicity of color in backgrounds (where the backgrounds themselves are pretty damn detailed) makes the whole scene appealing. The show's mix of 2D and 3D is also quite astonishing by 2005 standards, for a show that I can only assume had a very limited budget.
Relationships between characters change between episodes (refer back to continuity lapses), but they still remain relatively believable over time. While SNAFU's intentions don't really seem to have a point, neither do most bad guys in shows aimed for the family or kids these days; it's just something you can overlook when you learn to enjoy the characters themselves. Glowface is just so helplessly idiotic you can't help but like him, especially in his brief moments of sympathy when he's otherwise evil (yet very childish).
I recently saw the episode that supposedly never aired, "Theater of War/Breaking Camp", and it felt so good to see what I considered a "new" episode of The X's after over 8 years. It makes me want to try and at least get the show back into the public eye because, let's face it, the show was poorly received back in its day, and because it wasn't the gross-out kinda bad or the hyperactive/directionless kinda bad (just the "boring" kinda bad- codeword for "too much dialogue"), it was quickly forgotten.
I truly think that if people still remembered this show, new viewers would find it better than others did in 2005.