I have a lot of favorite modern cartoons (however, you're talking about since 2000; the cartoons I'm about to mention are since 1997)
* Cow and Chicken (1997, 4 seasons, 51 episodes)
(Hey, HPJD, you're in the UK, Cow and Chicken are REALLY big there aren't they?)
* Ed, Edd n Eddy (1999, going to be 6 seasons, going to be 78 episodes, going to be 3 holiday specials)
* Courage the Cowardly Dog (1999, 4 seasons, 52 episodes)