That's how fanboys are. One day they love something and one day they don't. I remember a time when Superman was considered a classic. Now it's considered an old movie with bad visual effects, Gene Hackman playing a wacky Luthor, and a cringe-worthy romantic scene.
There is also another kind of fanboy that seems to desperately cling to his/her preconceived notions, putting their own 'classics' on a pedestal while poking holes in anything new and/or superior.
My thought on this was over-looked, so I'll post it again. Yes, Joker is a more in-your-face character. But good acting, directing, and writing can allow for Batman to steal back the spotlight. In the `89 movie, look at the scene where Joker is dancing to Prince and destroying paintings at the museum. Yeah...Joker had his moments on the spotlight but arguably the most memorable part of that scene is Batman crashing through the window to save Vicki Vale.
In B89, the Joker was written as a fairly typical comic book baddie, with a standard doomsday plot. In TDK, he was written as the ultimate nemesis, un unstoppable force with no arc, no single super-grand destructive scheme and whose sole purpose in the plot was not to kill, but to push people to their breaking points at which they abandon all moral standards.
In TDK, Batman never had a scene where he stole back the spotlight. The closest was him flipping that truck but that scene will be remembered as a truck flipping over as opposed to Batman flipping a truck.
You and I must have watched two very different films then. Batman stole the spotlight from the Joker a number of times. First, at the penthouse where he takes down the Joker's goons and causes the Joker to flee while saving both Harvey and Rachel. Then of course, is the cheer-worthy reveal of the Batpod and Batman flipping the truck (yes, it will always be remembered as Batman flipping the truck because obviously the truck didn't flip by itself). Another instance is where Batman foils The Joker's plan to deceive the SWAT into killing the clown hostages. You can also see defeat in Joker's face when Batman's faith in the people on the ferries turns out to be justified - "What were you trying to prove, that deep-down, everyone is as ugly as you? You are alone." And let's not forget, arguably the most memorable moment in the entire film was when Batman beats The Joker's ace in the hole by taking the blame to maintain Harvey's reputation. Though he became a criminal with this act of self-sacrificing altruism, he also simultaneously turned into the definitive heroic figure of the film.
As mentioned in countless reviews, like The Empire Strikes Back, one of the things that TDK will most be remembered for is its powerful ending. And in those final moments of the story, it was Batman who was the real star of the film.