They Live tops the fictional-ads-in-sci-fi-movies list on Den of Geek. They didn't have Idiocracy in their top 10 list though; I would for reasons mentioned here earlier in Idiocracy kool-aid -- red or blue?
Fun details can be found at Den of Geek. Here's a clip from They Live, and remember you got to be good looking cause he's so hard to see:
Den of Geek also has: