I'm putting the same thread on multiple boards from our good ol' 90's shows. But anyway, what year did you think Nick started to begin to lose it's good shows and began putting garbage on? For me, I'd say 2001, after that Nick started to suck.
I would say around 2004 when "Hey Arnold!" and "Rugrats" were cancelled. "Avatar" was probably the only show on Nick that was actually a classic, but unfortunately, that was taken off eventually after the third season ended.
I'll say 2001 was when Nickelodeon went downhill. I don't think it can rise back up again either. Cartoon Network and Dianey Channel were still good for two or three more years. After that all them channel were terrible. Live teen tv shows now. Cartoon Network is not much of a children station anymore. It's sad what television become and we can't get back!
Nick started to tank between 2001-2002 but they still made decent shows like Jimmy Neutron, My Life as a Teenage Robot, Danny Phantom, and Avatar: The Last Airbender but around 2006-2007 is when it started to become completely unwatchable and what I mean by unwatchable I mean nothing good left on the channel worth watching. So really it's been crap for 5 years, not 10 years. But like I said it may not have been as magical like it was between 1991-2001 but 2001-2006 were still the Silver Age of Nick.