Commonly bad episodes (One Bad Apple, Boast Busters, Rainbow Falls) gave us good/important stuff (Babs Seed (song), Trixie, EG arc continuation.) Other bad episodes gave us absolutely nothing, so I'd remove them. The top three being:
Dragon Quest: Worthless, reinforces stereotypes, poorly characterizes everybody, dull plot, etc
Spike at your Service: Derails Spike, relies on poor characterization to continue the weak story, lame resolution
Owls Well That Ends Well: Typical cliche jealously episode
lol just realized theyre all spike eps.