OK, so we are talking 2008 movies in general and not Blu-ray in particular. In that case, I would pick the following:
1. Dark Knight (never changes from my top 1 list
)
2. Iron Man
3. Curious Case of Benjamin Button
4. In Bruges
5. Vicky Christina Barcelona
Note: I have not seen Milk, The Wrestler, or Slumdog Millionaire yet.