~ Reason why Itachi and Minato should never be compared ~
Itachi's intelligence is dwarfed by the 4th Hokage who was a genius on the level that only comes once in a lifetime. His accomplishments speak for its self, he reverse engineered the Bijudama and created the rasengan, he was the 2nd Kage ever to create a time/space technique through fuinjutsu, Hiraishin was so fast that he could literally kill an opponent in the blink of an eye, and with kushina's help created a jutsu that was capable of summoning the death god.
What has Itachi accomplished? Itachi was really good he sped through the ranks faster than kakashi, and was the greates Uchiha after Madara. Unfortunately the rest of the clan had grown weak over the years. The only reason Itachi is an S-rank-nin is because of the mangekyo and the ability to use it wisely under chakra deficit but it can't be used often since he doesn't have the necessary chakra to use it continuously.
In the end, there is no comparing them. Itachi is powerful but Minato is out of his league.
I see people say that Itachi doesn't have enough chakra all the time. While it's true his chakra is limited, all you have to do is watch his fight with Sasuke to see that he was capable of using quite a bit before he was completely exhausted of chakra. In this fight he probably used a bit more than he normally would, but he knew he was going to die so he was a little reckless.
However, he was able to use tsuki, various fire jutsu, susanoo, and amaterasu before he bit the dust.
Despite this I personally believe Minato to be the better shinobi, but their styles are quite different and they are hard to compare.
Of course I'd never do this comparison! Why would I compare a Weasel against a Port??
But yeah, I would personally pick Minato since he's got the advantage in speed (and according to the "Masked Man" fight, speed has SERIOUS ADVANTAGE). If Itachi used clones, Minato can use a tag to directly teleport behind the real Itachi, much like he did to Killer Bee and the Raikage. If not, he probably knows a bunch of sealing techniques that prevents Itachi from doing such a thing.
However, no matter how much info we get on a character, it's impossible to confirm who exactly is the strongest until Kishimoto officially confirms the line-up.