How about animated adaptations of the DC - Marvel crossovers?

[Hypestyle]

X-Men / Teen Titans

Superman / Spider-Man

Batman / Incredible Hulk

Green Lantern / Silver Surfer

Fantastic Four / Superman

I think it kind of goes without saying-- for now-- that any live action crossover films are off the table at Disney and Warner Bros.

However--

As we now see with this Batman/TMNT animated movie, DC/Warner is at least willing to explore animated crossovers with other properties (Paramount owns TMNT).

So in that vein, I suggest that something that DC and Marvel could and should look into involve animated adaptations of the established crossover specials that have been published over the years.

The basics of the story can be adapted, and expanded as needed to fit a 80 - 90 minute movie narrative. It would be up to the creatives, of course, but I don't think there should be any hangups about continuity and what stuff has been retconned (or not) since the original stories came out. They can still, for example, include all the original characters from the X-Men - Teen Titans story. The Superman/Spider-Man stories are the most dated, but Peter and Clark's career status can certainly be updated slightly.

[Kusanagi]

I'd love a JLAvengers animated movie, though that might be too history intensive to work.

[XPac]

At this point I'm doubtful we'll ever see it happen. The CLOSEST we MIGHT get is having marvel and DC characters both in a Lego movie.

That said, I think it would be great if it did happen. JLA/Avengers in animated for would be amazing.

[Midvillian1322]

WB ain't gonna let Disney and vice versa. Maybe if a third party got invovled

[DrNewGod]

The closest you're ever liable to see is if Marvel decides to put out a Avengers/Squadron Sinister film.