This is seriously tricky. This order could change on any given day, probably, but...

Guardians of the Galaxy
Iron Man films (no preference I can recall)
X-Men: First Class
The Avengers
Captain America: The Winter Soldier
X-Men trilogy (no preference I can recall)
Thor films (no preference I can recall)

As for DC, Batman all the way. The Dark Knight, Batman, I don't care if it's cheesy or serious it's all good. Watchmen has really interesting concepts and still gets me thinking and philosophising, but I just didn't find it that enjoyable to actually watch.