4. Its Mythology Was Actually Pretty Cool
In this corner of the DC Universe, awkwardly labeled the "Dark" series of titles, we learn that the basic elements of life are the "Green" (flora), the "Red" (fauna) and the "Rot" (death), all three of which are constantly in battle and threatening to upset a universal equilibrium. All three are portrayed as necessary elements for existence, with the Rot's crimes later on in the series not due to it being inherently "evil" but because it's knocked things out of whack.
While admittedly pretty fantastical, this goes a long way to string together some previously not-very-cohesive parts of the DC Universe, such as Swamp Thing, Anton Arcane and even Medphyll, that one Green Lantern who's also a sentient tree. The end result is a fleshed-out mythology that DC can pick up on, use and - knowing them - mess up at a later date.
3. It Had A Genuinely Great Crossover
Pretty much any modern crossover, be it Darkest Night or Siege or Flashpoint, suffers from almost exponential escalation where by the end the stakes are so high and the action is so huge that you can't really relate to them anymore - Dragonball Z Syndrome, for lack of a better term. The Rotworld crossover, co-written by Lemire and Scott Snyder, goes to some pretty extreme lengths, focusing on Animal Man and Swamp Thing's attempt to undo an alternate timeline where the Rot has taken over the world and turned everyone from Superman to Batman into Cronenbergian monstrosities.
As the two eventually set things right and restore the original, untainted timeline, it appears as though Rotworld is just as disposable an event comic as any other. But through it, Lemire and Snyder created a situation in which these two actually were important to the DC Universe at large; just not in the chosen one/linchpin/Kwisatz Haderach sense that permeates almost all superhero stuff, but by establishing that everyone in that world, big or small, has a part to play of some kind. That might sound like hippie nonsense to some, but it's a much-needed humbling element for a fictional world populated by literal gods.
2. It Was Actually About People
You'll notice that for most of this list, Animal Man has frequently been referred to by his legal name rather than his superheroic identity. It's not because "Animal Man" sounds dumb or gimmicky; if that were true we would also have to be ashamed to say "Batman," "Superman" or "Wonder Woman" out loud. It's because more than anything else, Lemire succeeded at making this superhero and his supporting cast feel like actual human beings - superpowered human beings, in a couple cases, but human beings nonetheless. It's about a dad realizing one of his children will do greater things than he could ever hope to aspire to; it's about a brother envying his sister for powers he'll never have; it's about a mother torn between her love for her husband and her desire to keep her kids safe at all cost. Most of all, it's about a family in way over their heads, pursued by forces that might unnerve even Superman, and doing their best to keep each other alive.
All superheroes have loved ones to keep them grounded: Superman has Lois Lane, Spider-Man has Mary Jane, the Punisher has - well, had - a family. But when those supporting characters are in danger, it's primarily to add tension to the plot and give those heroes something to fight for. With Animal Man, Lemire developed the Bakers so well that when one of them is in danger, it isn't a promotional stunt: it's the very core of the series. Reading his more realistic, family-centric works like Essex County and The Underwater Welder, it's not surprising that he brought that element of intimacy to Animal Man, but it is something relatively unheard of in the realm of mainstream superhero comics. And without his human touch, we probably wouldn't have moments like this.
1. Socks the Cat
Look, the Lying Cat from Saga is cool and all, but she ain't got nothin' on Totem of the Red-turned-housecat Socks. Not since the little Arquillian dude from Men in Black has a character shorter than two feet high carried on with so much gravitas.