While I always had a bit of a problem with the original slogan of Newgrounds - it sounded too... apocalyptic. Still, it was bold. BOLD is the thing that, I think, best defines Newgrounds - even more so than the fact that it's got just about everything by just about everyone. The new slogan, while shorter and nicer, doesn't have that bold feeling to it. I realize that you wanted to take away the "angsty" feel of the site and make it more of a "creative community" than a... well, you get the idea. I, alas, didn't find Newgrounds until a couple years ago, so I never saw what it originally was like.
While I DO think that the slogan should be changed to something else, I think that "Everything, by Everyone" is a little too weak. It needs (in my opinion) to be something bold and imposing, but still indicative of what this site actually is. I think that the original slogan should actually be truncated to something like "The Future, Today!" It's short, sweet, and moderately bold, with an almost playful feel to it at the same time. It doesn't shine a negative light on the site while still hearkening back to the original slogan as well. However, I have a feeling that something that simple has probably already been used before.
I'm concerned with how Newgrounds seems to be drifting away from its roots, though. A friend of mine commented on how the site seems to be going corporate or something. "The beginning of the end," he called it. I like the idea that Newgrounds is moving towards becoming cleaner and more streamlined, both in appearance and operation. I know that the actual content of the site isn't going to change, but the theme of the site is being drastically changed from a host of radically-minded people to the web's largest showcase of animation talent. In that sense, the change is good. Newgrounds shouldn't completely forsake its past, however.
Damn, I type too much.