What PG or PG-13 movie would be made exponentially better...

The Hunger Games.
Divergent.

 

Going out on a limb here... Tim Burton's Alice in Wonderland (2010, the live action flick)

 

After recently watching it, I'd say 3 Days to Kill would have been much better if it were R-rated.

 

Its already pretty rad, but possibly, POSSIBLY an R-rating could somehow make Pacific Rim even greater than it is.

In my personal opinion (I've read the book, btw, recommend it!) I think The Mortal Instruments: City of Bones could have done alot more stuff with the monsters and action if it was R.

Oz the Great and Powerful. Or really just any Oz movie. It's just the kind of thing that- if you took off the "EVERYTHING MUST BE SAFE" rating, it could have some REALLY cool stuff in there.

 

Harry Potter. If half of the crazy shit that were present in the books were invoked into the movies, they'd be way better - and that's coming from someone who's already an avid fan of the series over all mediums!

 

I would have just loved to see actual children cast as Katniss, Peeta and Gale instead of adults.  It could stay PG13 and still be more impactful.

So I am going to continue with the book theme and say Sisterhood of the Travelling Pants.  Now this isn't to say that I actually believe that the material in the book is all that 'mature'.  The books did deal with issues such as mental illness, suicide, pregnancy scares, aging and cultural barriers a lot of which was dropped to make a lighter movie.  (Also female sexuality which of course means it needs to be bumped to R.)