There are some first-rate parody segments on The Simpsons but they almost always feel out of place... as if the writers want to work on Robot Chicken or something instead but they're stuck on The Simpsons so they try and retro-fit that stuff into an episode.
I think Angry Dad: The Movie was more parody filler than episode - they had lengthy segments lampooning Wallace & Gromit, Toy Story, The Triplets of Belleville and Persepolis. The Simpsons content felt like an afterthought and even then they managed to free up two minutes for Ricky Gervais to monologue in his self-deprecating, unfunny fashion.