Here's a funny "Infographic" about Cannes from the ever reliable Onion.com:

Dragun pardon Monsiéur ..BUt can you explain to me what the humor is supposed to be ?...I find it too dry indeed and ...

Haha, okay, I'll attempt to explain the titles.

Efficient and Efficienter (Germany)- the stereotype of Germans is that they are very task-oriented, efficient people.

Les Busters Des Ghosts (France)- It's just "Ghostbusters," man!

The Sombre Hombre (UK-Mexico)- Nothing sophisticated here, its just something silly. Note the British spelling of "somber." It is either really spelled that way in the UK or just a parody of how other English words, like "center," are spelled that way.

Turkish Batman (Turkey)- It's Turkish Batman, need I say more?

Grey, Grey, My Passion (Russia)- Aren't Russian films seen as kind of bleak?

Hot Shots! Part Trois (US)- See "Hot Shots! Part Deux"

Screwed Up Nutballs II: Spring Break Fever (US)- We see too many of these stupid teen films from the US, and its funny that they would submit this to Cannes.

As for the ones I didn't explain, I don't know why they should be funny.