If all-ages TV animation went from marginalized to mainstream in the '90s, the genre went from mainstream to ubiquitous on the '00s. The old standbys were already there from the previous decade, including "Family Guy" and "Futurama," which both premiered in 1999, but thanks to Comedy Central and the Cartoon Network, particularly the late-night Adult Swim block, the diversity of styles and tones were ever expanding.
 
Adult Swim, in particular, probably deserves some sort of recognition or placement on a list like this, as it premiered in 2001 and gave a home to everything from "Aqua Teen Hunger Force" to "Space Ghost Coast to Coast" and "Harvey Birdman: Attorney at Law," plus imports like "Cowboy Bebop" and  "Bleach" and non-animated offerings like "The Mighty Boosh." If I were feeling edgy, I could have given this slot to "The Venture Brothers" or to "Squidbillies" and laughed maniacally. 
 
I'm not feeling edgy. [Or maybe it's just that while I've watched, and often enjoyed, episodes of every show I just listed, I'm not a regular enough viewer to feel like committing to putting any one of those shows. Also, I have a bit of a cheat coming up in a few days, so I didn't want to cheat by saying No. 22, "Adult Swim." Gotta keep the cheating to a minimum.] 
 
But consider this to be a dully noted tip of the hat to Adult Swim and the very profound impact it has had on the media landscape for a very specific demographic (as a commenter pointed out, that demographic was expanded by the erratic, but sometimes awesome "The Boondocks").
 
I hate to be unhip and retro, but as much as I *really* liked "Futurama" and as much as I *sometimes* liked "Family Guy" and as much as "South Park" reliably drops one brilliant episode per season, my favorite animated show of this decade is the same as my favorite animated show of the last decade.
 
Coming in at No. 22 is "The Simpsons."
 
[Justifications and contemplations after the break...]
 
I didn't make a list like this in 1999, but if I had, I don't doubt that "The Simpsons" would have come in at No. 1. Springfield's most beloved animated family wasn't just the best show of the '90s, it was also the defining pop culture text of the decade. 
 
When the alien invasion happens and humanity is wiped out and you're walking the post-apocalyptic wasteland with your small scrappy child, dodging zombies (don't ask why there are zombies in the aftermath of the alien invasion) and trying to keep alive and the kid says to you, "Daddy [or Mommy, as the case may be] what were the '90s like?" what DVD are you going to whip out of your rotting leather satchel, stained with sweat, tears and blood? Yeah. That's right. Season Four (or your favorite) of "The Simpsons." No question about it, right?
 
There's been a familiar online trope that goes something like, "'The Simpsons' sucks. It hasn't been funny for years. Blah blah blah." The trope has been popping up since like Season Six. 
 
While that sentiment is hyperbolic, I'm not going to argue with a main thesis: "The Simpsons" is never going to be a funny as when you first remember experiencing it. 
 
Part of that is that after 450-ish episodes some sameness has set in with the plotlines. A movie films in Springfield? Again. Homer gets in shape? Again. Bart gets his first girlfriend? Again. Marge gets tired of being a housewife and gets a new job and Homer becomes intimidated by her success? Again. 
 
Part of that is that with 85 other animated shows all rushing through plotlines the old rule "'The Simpsons' did it first" is still *mostly* true, but it's not the industry standard anymore. Every once in a while, "The Simpsons" now does something that "South Park" may have touched on previously. It hasn't happened that often, but every time it does, it makes me a tiny bit sad.
 
And part of that is just that, again, after 450-plus episodes, how could anything fresh and rule-breaking seem quite as fresh and rule-breaking?
 
So no, "The Simpsons" is no longer as good as it was in 1994. That's why it isn't No. 1 on this list of TV's Best of the Decade. It remains, however, smart, savvy and endlessly rewatchable (albeit perhaps a little bit less each year). And no, the show doesn't turn out 10 or 15 classics per season anymore, but if you look at the 213 episodes that aired in The Aughts, there are definitely enough classics and near-classics and near-near classics to justify being at No. 22.
 
What am I counting as classics? Clearly some of these will be episodes that you might not have enjoyed as much as I did, but pick a few from this group: "Alone Again, Natura-Diddily" (the death of Maude Flanders), "Missionary: Impossible" (fun with Jeebus as Homer becomes a missionary), "Behind the Laughter" ("Behind the Music" parody), "The Computer Wore Menace Shoes" ("Prisoner" parody), "Worst Episode Ever" (Comic Book Guy has a heart attack and the show gets extra-meta), "Tennis the Menace" (one of the strangest cold-opens ever leads to the Simpsons getting a tennis court), "New Kids on the Blecch" (boy band parody with N'Sync guesting), "Hungry, Hungry Homer" (the Isotopes might move to Albuquerque), "Trilogy of Error" (structural fun as the same story is told three ways), "Homer the Moe" (Moe redecorates the bar and explains post-modernism), "She of Little Faith" (Burns buys the church and Lisa doubts her faith), "Tales From the Public Domain" (vignettes the writers didn't have to pay for), "Blame it on Lisa" (Brazil is FULL of monkeys), "The Sweetest Apu" (Apu has an affair and has to get-right with Manjula), "I'm Spelling as Fast as I Can" ("And a hotplate!"), "Three Gays of the Condo" (Homer learns what it's like to be a Homersexual), "Half-Decent Proposal" (Sepinwall's favorite episode of the period), "The President Wore Pearls" (sharp "Evita" parody), "Bart-Mangled Banner" (Marge accidentally says Springfield hates America), "The Seemingly Never-Ending Story" (another piece of fragmented storytelling), "Kiss Kiss, Bang Bangalore" (Homer goes to India), "Moe 'N' a Lisa" (Lisa turns Moe into poet, with guest voices including Tom Wolfe and Gore Vidal), "Springfield Up" (parody of the Michael Apted "Up" films), "24 Minutes" (solid "24" parody), "Husbands and Knives" (only for the rival Comic Book Guy), "Eternal Moonshine of the Simpson Mind" (still more narrative fragmentation), "E. Pluribus Wiggum" (a rare Ralph-centric episode), "The Debarted" ("The rat symbolizes obviousness!"), "Any Given Sundance" (a "Capturing the Friedmans" parody? NICE)... Etc.
 
I'm stopping there, just because I always feel that it's hard to judge a "Simpsons" episode if I haven't seen it a couple times and most of the newer episodes I've only seen when they first aired. Some of those episodes, you probably didn't care for. A handful of the episodes that I didn't mention, you probably adored. There's a lot of terrain to cover with that many episodes.
 
One can see that "The Simpsons" continued to tackle religion, politics, mainstream pop culture and even obscure corners of the media in the Aughts.  The guest voices were higher profile and also more absurd than ever before, with everyone from Tony Blair to Simon Cowell to Mick Jagger to Will Shorz to George Plimpton to Yao Ming lending their pipes. The show even expanded to allow for several guest writers, with Ricky Gervais and Seth Rogen writing episodes (not the best episodes, but still...).
 
It's possible that "The Simpsons" became more politically outraged than ever before in the waning years of the Bush Administration, finding pointed ways to target the supposed death of political debate in the country, as well as the decline of certain basic personal freedoms. At times, the show even seemed angry, which wasn't always a boon to the humor, but it was a reminder that Al Jean and his team of writers aren't just a factory pumping out episodes. 
 
Plus, "The Simpsons" got a new injection of creative spirit when the show shifted to HD last season. In addition to prompting a redesigned and even funnier title sequence, HD gave the show more real estate for sight gags, leading to episodes that are even more pause-worthy and rewatchable than ever before by virtue of the number of added details. The animation is bolder and more colorful than ever before, even if it isn't quite on the level of vintage "Futurama" episodes.
 
[It has no bearing on this list, but "The Simpsons" also did the near-impossible during the decade: The show put out a feature length movie, something most fans had begun to believe would never happen. And even more incredible than that? The movie didn't suck.]
 
"The Simpsons" has been victim to a hyperbolic rush to go from love to hatred when something slips from the pinnacle to the upper slopes. When I went through the episode list for the 10 seasons were there some real stinkers? Sure. Were there more than in the first decade? Yes, but maybe not by such a large amount. Were there more episodes that were just "good" or "diverting" rather than "very good" or "excellent"? That sounds about right. 
 
Over 213 episodes for the decade? I got enough pleasure to be happy with "The Simpsons" at No. 22 on list of TV's Best of the Decade (and I probably could have gone higher.
 
Up tomorrow? It's odd, but only one writer-producer has two shows on my list, two shows that he-or-she is seen as a driving creative force for. That person's first show on the list appears tomorrow.