Marvel:

1. Iron Man
2. The Avengers
3. X-Men 2
4. Thor
5. X-Men First Class

Number 5 was tough and could be any of several on a given day, the rest were easy. There are plenty of other good ones that aren't on my list: X-Men, the first two Spider-Man movies, Captain America: The Winter Soldier, X-Men Days of Future Past, Guardians of the Galaxy, and really any of the recent Avengers series movies were decent.

DC:

1. The Dark Knight
2. Batman Begins
3. Watchmen
4. The Dark Knight Rises
5. Batman

Really other than Watchmen there have been no good DC movies outside the Nolan Batman trilogy.