Out of the four miniseries leading up to Infinite Crisis, the most interesting story wasn't even one of them... it was the four part Power Girl tale from JSA Classified #1 through #4. DC should have pumped that story up a bit and made it one of the hyped minis... it would certainly have been a better choice than that terrible and pointless Rann-Thanagar War.
PG's big problem is that she has never been a marquee name; therefore, no new mini. Post-Crisis, her widest fame came during the JLI/JLE years, when she was largely used as a one-note "bitch" character with a pet cat and a diet Coke addiction. She's had several origin revisions since then - which is why the Classified story was so good, because it directly referenced the confusion surrounding her. Plus the art was great, super-heroics with an indy vibe. I thought it was a fantastic fresh take on the character, because she hasn't exactly been well-used in JSA since she joined a few years ago anyway. In JSA, she's just another token strongman. In JSA Classified, we saw her as a person, which was, for me, the first time since, well, ever.
That story led directly into Infinite Crisis #2, where we finally hear her true origin: the same one she had when she first appeared, back as part of Earth-2. She remains as she was then, the cousin of Earth-2's Superman... the mirror analogue to Supergirl being the cousin of Earth-1's Superman.
Of course, post-Crisis, all Supergirls of any stripe were wiped out. And that decision was made with good reason... because it becomes increasingly stupid for Mr. Last Survivor of Krypton to also have a Kryptonian cousin, a Kryptonian dog, a Kryptonian city-in-a-bottle, and a baker's dozen of Kryptonian villains. It just eats away at what makes Superman Superman. So while Supergirl herself died during the Crisis, somehow Power Girl survived into the new, One Earth universe... but she needed a new origin to take her away from her former Kryptonianishness. Which is why we had all the confusion as new creative teams tried to make her new role make sense... she's super-strong, she can fly, she can go toe-to-toe with any number of other DCU powerhouses. She's too big to ignore. (Alex Ross made her one of Superman's key lieutenants in Kingdom Come!)
And yet, even though the concept of "Supergirl" was more or less off-limits to poor Karen Starr, other people were pouring out new Supergirls all over the place. Not too long after Crisis, a "Supergirl" showed up who was actually an alien shapeshifter who modelled itself after Superman. A brunette Supergirl walked into Action Comics one day claiming to be Clark and Lois's child from the future. And now we have the sexy Michael Turner version from an arc in Superman/Batman, who, I guess, is the new "real thing." (Great Wikipedia article here.) Eh. The whole Super-Family concept annoys me.
So the notion that Power Girl is a lost fragment of pre-Crisis continuity is cool. It's like a meta-origin. We fans all know of her Earth-2 days, even though they were wiped by Crisis on Infinite Earths... and now the hook of Infinite Crisis is that the Golden Age Superman wants to bring it back.
There's a bit in IC #2 where Kal-L, the Original Superman, reflects on what has happened in the DCU since Crisis. Doomsday. Knightfall. Emerald Twilight. OMAC Project. Among others. It's more or less a Greatest Hits cavalcade of DC's big event series over the last twenty years. (GA Superman must have passed over such pseudo-event flops as Bloodlines, Underworld Unleashed and Eclipso: The Darkness Within.) His point is that the current DCU is dark, brutal and undeserving of having won dominant status after Crisis... which is actually a bit misleading, since it wasn't just Earth-1 and a couple of -2 longshots that survived... the "new Earth" was supposed to be a gestalt of five Earths: 1 (Justice League), 2 (Justice Society), 4 (the Charlton heroes), S (the Shazam family) and X (the Freedom Fighters). Classic Supes is looking at the world through rose-colored super-glasses when he posits that an Earth-2-dominated universe would have turned out better.
I always thought the merging of the Earths was rather even-handed. The biggest losers of Crisis were the hitlisted duplicate characters and anyone connected to them. Like Earth-2's Robin and Huntress, grown adult heirs to the Golden Age Batman's legacy. GA Bats had died several years before Crisis, neatly removing him from the stage, so Robin and Huntress were crushed into oblivion during a shadow demon battle. The Golden Age Wonder Woman was quietly shipped off to a far corner of Paradise Island, and then her role in the JSA was later retconned into Hippolyta herself, who wore the Wonder Woman mantle 40 years before Diana set foot on "man's world." And, of course, the original Superman, whom not even DC's editorial staff could kill during Crisis. He was hidden away in a pocket dimension and assumed to be one of the final continuity taboos.
Until Infinite Crisis.
But you can see why DC did that... having extra versions of the big three running around, with history set squarely in World War Two, is a major drag around the necks of the characters as they exist today. Especially since the difference between Earth-1 Superman and Earth-2 Superman is damn near nothing, certainly not as obvious as the Earth-1 Flash and the Earth-2 Flash. Of course, the real reason behind that is that the big three were in continuous publication from the '40s through the '60s and into the '80s; they were never "reinvented" as were Green Lantern and the Flash into completely different characters. So when fans demanded a logical continuity between all the characters, there was just no way to have one single Superman or Batman or Wonder Woman explain away fifty years of stories.
It was a mess and Crisis on Infinite Earths was a brave idea, and the right thing to do. That's what makes Infinite Crisis so exciting, because of the threat to undo all of that... and with the World's First Super Hero cast as the antagonist! (And he has Superboy-Prime with him, who will probably get a sound drubbing before this is all over. I've never understood just what his deal was back in COIE, and I even have that crossover issue of DC Comics Presents that was supposed to explain it.)
You just have to wonder how all this will turn out for Power Girl.