I think the best years where the one from the half of the '90s till 2003-2004s. We had Pirates of the Dark Water, SWAT Kats, Dexter's Lab, PP Girls, Samurai Jack, MEGAS X.L.R. , Justice Leage, Batman series, etc. Now we mostly have crud, though I find Camp Lazlo really entertaining.
Dunno if Im a black sheep in the crowd but I really liked Reign: The Conqueror. That was more of a late night adult swim show though.