Here's my interpretation on the whole "strongest" Hokage thing. It was said by Iruka, and also in the data books (apparently, I haven't read them myself so I take the words/quotes of others) that Hiruzen was the strongest Hokage. Despite this being said in the data books and in the series, I believe that Kishi has contradicted himself, and has lead us to come up with different assumptions of the "strongest" Hokage.
What I mean by this is that, in the first series (before Shippuden) and in the first data book (which also corresponded with the first series at that time), yes it may have been Kishi's intent to say that Sandaime was the greatest Hokage, and what we've seen of him past his prime, leads a lot of people to believe that he was even greater then every other kage before him (the fact that he faced a Sannin, and the two previous Hokage. Even if they were edo summons and weren't in conscious states of mind). However in Shippuden the plot has thickened, and there are a lot of aspects that he adds in in order ot make the series a stronger story. He's giving this action based manga and anime some thick situations and scinerios in order to make it interesting...however, by doing so he has given new implications on certian things (i.e the Hokage topic we're on right now) that he didn't give, or gave the opposite of in the first series. Don't get me wrong there isn't anything wrong with that, and we have to give him credit for doing the great job he has done for so long (this must be complex for him to do).
What I'm getting at is, what was acceptable, or stated in the previous series or in the past, may not hold true today in his mind. It could also be that he had to contridict himself for some reasons or another concerning the series to make it more climatic and have it build up...that means the Kage. So far there is no recent data books up to the series, but does everybody know how the stats for the main characters get upgraded (more or less) in each book that has came out? That is similar to my theory on what he's doing with some things in the seires like the Kage. In part 1 we only knew of Minato as the guy who saved the village from the Kyuubi...in this part we found out just how he did it. He defeated Tobi in a short time and saved the entire village from the Kyuubi almost single handedly. We saw how he did this, we saw him take down a shinobi many believe to be the strongest at this point in time. We've seen demonstrations of his skills and so much hype that has crept him up and made people think of him as the greatest shinobi...now with Hashirama...Now I forget where it was stated that Hashirama had fought and defeated Madara (I believe it was part 1 because of the whole Valley of Ends deal)...Madara Uchiha, the man who has gained EMS and was saw as the most gifted of all the Uchiha. We see him now and we are getting his demonstration of power. Now with that, the questions pop up "how did Hashi defeat madara?" and "Hashi is the greatest if he defeated Madara"...this is a lot of hype but it might be well placed. I doubt Kishi has forgotten how he said Hashi had been defeated so all this does is boost hashirama's...Many think that Hiruzen could never have beaten Madara and therefore Hashirama is greater then him because He did in fact defeat madara
To prevent a long ass ramble which I know I'm doing, I'm going to cut to my main point...
Kishi says things...but implies other things later on, for the benifit of a greater action and stronger story...it may show flaws and contridictions to what he's said before but sometimes that's neccessary. However, this conflict over "Strongest" Hokage can go either way really. Hiruzen's debut as stronges Kage was in the verry beginning, and no implications sense his fight with Orochimaru has hyped him or repped him. It was said in a data book that came out in the time of Part 1 as well...In part two we see Minato's admirable and powerful skills, and we get the implications of Hashirama's power by looking and comparing them to Madara's demo right now. Tobirama even has his little bit of power hype creeping up. Edo Tensai, despite the description saying he didn't complete it, shinobi of his time (such as Muu) knew of it's existance and it's power. Madara has recently demonstrated knowledge in it. Gaara's father knew about the justu as well (even if he was a more modern Kage). The rep he gains from this show that...it had to have had some level of control or usage of the jutsu...not to mention Minato's brief comentary on his ST jutsu. Add that to the incredible water jutsu and he has been hyped to be a very powerful character as well. Do people see what I'm saying here?
I just felt like writting, don't complain. If you have a problem with it, don't read it and don't comment.