I think that the crossover The Black Prince would definitively find some success on the big screen- or at the very least, as a tv series, given how beloved both Harry Potter and ASOIF are atm...

 

The Lie I've Lived could be a great comedy flick, just imagine the scene where Harry discovers he remembers his father's life.

Oh wow that's so cool.
Omg that's my mother.
Cringe.

 

I know people are gonna be mad at me but I have to admit that I like the idea of Methods of Rationality. I think it would make a pretty interesting movie, though I have to admit that their are other fixes that would definitely do better. But still, their are alot of scenes that would make great scenes in a movie and I think it would be more of a scary movie style parody, but with a more intelligent actual story under it. Still, the Scarry movie franchise is pretty damn successful, and I realy think MoR would be alot better then thst bs

 

Well, judging by Cursed Child, apparently any old fanfiction can be made canon/into a movie.

But, to add my own 2 cents, I think Browncoat, Green Eyes could do quite well. Not as an action story but more as a thriller/drama with maybe a bit o an adventure thrown in as Harryan co try to figure out what happened to the Wizarding World.

 

Probably a black comedy, it would certainly have to be quite Au and not simply a retelling of cannon with one minor difference.

 

There are so many listed that I haven't gotten around to yet but from the few I've read I think Prince of Dark Kingdom would be a pretty epic series to make into a movie. Plenty of action, good characters, and of course an interesting plot.