All the phases of CN, it's crazy and depressing to think about. First the Cartoon Cartoons like Dexter's Lab, Cow & Chicken, JB and late nights with Space Ghost C2C and Cartoon Planet. Then came the Toonami era, those Toonami promos were seriously sick. As well as Toonami, Hanna Barbera was still churning out shows like Powerpuff Girls, Courage, Samurai Jack, Billy and Mandy, Fosters. Then came the Adult Swim era with their original lineup of shows like Spaceghost reruns, sealab, aquateen, home movies. Toonami added Saturday nights, then died and eventually came back, but a lot of good shows were shown in late night Toonami. The death of good daytime cartoons came with stuff like total drama island. Then the rebirth of daytime cartoons with adventure time like 5 years ago. Now there are a lot of good toons on during the day. There was the evolution of Adult Swim. Adding all sorts of interesting programming for all types. Absurd humor with Tim and Eric. Stuff like robot chicken. The addition of Family Guy and KotH. (Not sure if these count as syndicated).
This is not an entirely accurate timeline, it jumps around a bit, but this was pretty much my periods of watching Cartoon Network. There were good shows sprinkled throughout the timeline that were not mentioned, but there was a time there I wouldn't want to turn on CN during the day.