Disney's Doug - I only saw a couple of episodes of Disney's Doug, but based on what I have seen, Disney's Doug was even more painfully Politically Correct than it's Nickelodeon predecessor was. Plus, I didn't much care for the changes made to the cast.
All Grown Up - BrendaBat crystalised my thoughts about AGU to a T. Nick should have left AGU as a one time only special. Turning it into an endless series was overkill. At least when the Rugrats characters were babies/toddlers, the show had an original premise. As tweens, the show was just a carbon copy of every other tween comedy that was airing at the time. Plus, it made no sense that the main characters were between 10 and 11, yet they acted like teenagers. The only characters who are excused are Angelica and Susie, who actually were teenagers (they were 13). The only good thing to come from AGU was that here, Dyl actually had a personality and wasn't just a walking poop joke.
Ren & Stimpy: Adult Party Cartoon - The post Nickeloden R&S shorts were awful, disgusting, nauseating, crude and worst of all, not funny. Half way through the short "Fire Dogs 2", I stood up and said "Done!".
So, as a choice of the 3, I guess that Disney's Doug wins, but by a very small margin.