Gen 1, no contest.
Controversial opinion but I'm not sure if Gen 3 was worse than gen 2. Pretty much all of season 4 is melodramatic and depressing af and season 3 had some very questionable episodes and concepts (who remembers Freddie's sister being on a talent show?
)
Although Gen 3 had some shocking eposodes some of gen 3s episodes were actually really good.
All this said I have a special place in my heart for Skins. It wasn't your typical shallow teen drama and explored issues you wouldn't see elsewhere and weren't afraid of being conceptual here and there.
Also, Sid was always the best character.