The first one I can remember was pokemon (the first movie). It was so powerful when Ash was brought back to life by all the pokemon (good and "evil"). Of course I was like 10 when I saw it ^^ so maybe it wouldn't be as moving now.
Other movies I cried in that I remember were Erin Brockovich, A Walk to Rememeber, King Kong (the new one), Click (lame i know)...ohh and Lion King every time
My bf got Dream Boy so we can see it tonight...hope its not that sad.
Edit: Another one that I watched a couple of times and then showed it to my friends to see if they would find it powerful too was "Alphadog", which is based on a real story and has some pretty good performances (especially by Anton Yelchin, Justin Timberlake and Sharon Stone) and also touches on some really tough topics that are so common nowadays like parents not being responsible about their kids or not listening to them. There's also drugs and reckless partying that are cause of rich teenagers having too much time on their hands and no one to stop them....I dunno lots of stuff lol. I think its pretty good AND it has some hot boys and girls in it ^^