I have no problem crying at ALL, my depression + sad movies take care of that. I have the following levels :
Level 1 : Teary eyes.
Level 2 : Tears running slowly down my face.
Level 3 : Steady stream of tears from both eyes.
Level 4 : "The Waterfall", I can now barley see anything.
Level 5 : "The Waterfall" + sobbing +
complete loss of control.

(a bit scary)
I actually grade sad movies on IMDB depending how high I get
Movies that trigger a high level for me, are movies where kids die :
Hotaru no haka (1988) (my only Level 5 so far)
My Sister's Keeper (2009)
Freedom Writers (2007)
The Ultimate Gift (2006)
Bridge to Terabithia (2007)
or where people are dying for someone/something they love :
The Last Samurai (2003)
Man on Fire (2004)
Léon (1994)
--------------
From the mighty Internet :
Tufts Daily - New research questions benefits of crying
"The University of Florida study also indicated that individuals with mental health problems such as chronic anxiety are unlikely to experience benefits from crying.
Willard agreed that for those with more depressive tendencies, crying might not bring any long-term relief."
Hmm, interesting, I don't feel any better after crying, I just feel empty. Maybe I'm an emotion junkie ?!