This is a really interesting question. Cryptography, I think, is shrouded in uncertainty. History is riddled with instances where the world 'knew' that their method of encryption was completely secure, only to discover years later that wasn't the case. Usually once they were in jail, or the war was over already.
You see.. Eve (the nickname we give to the person trying to evesdrop in Cryptography http://en.wikipedia.org/wiki/Alice_and_Bob), is at an advantage if she knows how to decrypt a message if Alice and Bob don't know she can. Because they will continue to communicate while she eves drops.
While a little out of my depth, people are well into the realms of Quantum Cryptography. Which as Simon Singh explains in his book 'The Code Book', will really blow most currently known encryption methods out of the water. Even if we were to simplify this, hackers are now using cloud architecture to increase computing power massively to decrypt information.
You only have to look at the competitions held at conventions like Defcon every year where the competitors seem to have machines and resources 10 times what they had last year :)
You could possibly argue, that as time has gone by code breaking has become just as much about computing power as it has about the method of decryption itself. I.e. it doesn't take a computer to break the Casesar Cipher (http://en.wikipedia.org/wiki/Caesar_cipher) but you better hope you have some computer power to break say, MD5 or DES.
In that sense, it's hard to answer what the most secure method of communicating is right now.. We can't be 100% safe in the knowledge that publically known encryption methods can't be broken.
So how can we securely communicate in the real world? Well.. I think we need to consider the very first communications.
Assuming it's true that, given enough computing power, AES256 can be broken.. commonly considered 'military grade' encryption, I think we need to focus on other means of being safe. I think that is in the initial communication. If you assume we're utilising public key bases ideologies, once each person has the key, they need only send encrypted messages without the key. Some communications lend themselves well to that, I think.
PGP encryption is good I think. Because you can physically pass the key on a piece of paper, memorise it, which you can later burn, for example.
I quite like OCR (http://www.cypherpunks.ca/otr/) which is similar but also integrates with a few instant messaging programs.
tl;dr ultimately nothing will always be secure, if trends in history prevail. But something where you can share a key and never repeat it out loud is possibly about as good as you can get right now.
p.s. i'm no expert. Just sharing what I know :)