@SpeedForceSpider: It's unlikely he would use Izanagi or Izanami because of their terrible side effects. They're really desperation moves because once you use them, you lose one of your eyes. For a sharingan user who relies on his eyes a lot, you can imagine how bad that would be and neither of the moves guarantee success.
Also before anyone questions me, Itachi is my favourite character so I'm no fan wanking Minato or anything here just saying it as I see it.
@GIRUGAMESH: I agree with your feats>statements but when the statement is made by the enemy then I don't see how that works. Why would any enemy go out and say something that doesn't benefit them in any way or form. Surely not just for the sake of talking. 3 of the most powerful members in Akatsuki admitted that Jiraiya would beat them.
I can understand where you're coming from when you say you would like for there to have been more feats shown, but even so from the feats shown he's been able to take on 3 very powerful ninja and beat them in 1 hit. Speed wise, he's easily the fastest character seen in the series other that possibly current Naruto. That was stated by none other than the Raikage, who is one of the fastest characters. Raikage stated that even with his with his lightening release armour enhancing his speed and reflexes he was still outmatched by Minato. Now we know how Raikage was totally blitzing Sasuke during their fight and although Itachi is possibly a little bit faster than Sasuke, I doubt he is THAT much faster than Sasuke. Battle intelligence wise I would say they are both equals and are both probably the most intelligent ninja in the series so far.
The only thing that would give Minato trouble is Susanoo, because like you said he would have difficulty getting past it. But like I've said Itachi can't keep it up for long. Also like you said if it was a real fight, Minato would probably have a technique for it.
Whether Pein could take Minato is another debate all together. Personally I think Minato could take him, provided he was fighting all 6 forms at the same time. If he didn't know the technique then he would probably fall in a similar way to Jiraiya. Speed is the key with Minato, as has been shown so far. He can take out a high class ninja in seconds, in fact I would say he would probably have a harder time with someone like Itachi than he would with Pein (mostly because of Itachi's intelligence).
I doubt the jinchuruukis would pose much of a threat, they've been taken out by various Akatsuki members like Deidara, Kisame, Hidan + Kakazu etc.
Edit: IT would definitely be a close fight. There's not many people imo who could threaten Minato like Itachi.