I would agree that WrestleMania XX when the title headlined the triple threat between HHH and Michaels, two of the biggest names, ever, and Chris Benoit, who was definitely, at least at the time, the most underrated wrestler in the world.
When it was the Raw title, it was important. When you're being chased on the A show, then you're the A title. It was arguably revolved around the biggest names, when Triple H was running rampant across the WWE and JBL was headlining Smackdown shows.
The WWE Championship took it back when Brock was wrestling for it, IMO. As much as the legacy of the WWE Championship has been diminished in the Cena Era, especially in recent years, CM Punk isn't defending the WHC at Mania; he's the A champion, so he's got the A belt and that's where the WHC is left. I sort of feel like the WHC is the new Intercontinental Title. It's presence has made the IC less valuable, because it has become the pinnacle of young, sort of middle card champions. Cody has done a good job to try and keep the IC relevant, but what happens when he moves on to the WHC or even the WWE Championship? Who's going to keep that belt relevant, Ezekiel Jackson?
The WHC has hit it's pinnacle, the two world titles novelty has worn off, and we need to go back to just one in order to make the WWE Champion look stronger. I'd rather have one crowning achievement than two pats on the back. I know this isn't the right place to lobby for this argument, but I feel like it's relevant, here.