2 week itinerary review

I will be arriving at Haneda Airport October 2nd, and departing from Narita October 16th. A rough outline of my trip is:

Oct 2nd - Oct 8th: Tokyo, possible side trips to Nikko/Kamakura

October 8th - October 13th: Kyoto, side trip to Nara and possibly Arashiyama

October 13th - October 15th: Osaka

October 15: Leave Osaka, return to Tokyo

October 16th: Depart Tokyo

I think I may have allotted too much time for both Kyoto and Osaka but I'm not sure. My gut instinct is that I'm more interested in the big city (Tokyo) than more historical stuff, though I'd still like to see some temples. Does anyone have ANY thoughts at all? I'd be happy to hear any suggested changes to dates, specific things I should make sure to see, places to make sure to eat, anything like that!

Looks decent enough. If don't want to pack up and move so often, Osaka and Kyoto are close enough where you can make base there for your Kansai travels.
I'm assuming you'll be using a 1 week JR Pass, as that will pay off for your Tokyo - Kansai round trip!

If your main interest is the big cities then definitely put more time into Tokyo and Osaka and also plan a day trip to Hiroshima. I'm also a city guy and two to three days in Kyoto would be enough in my opinion.

If it was me I'd be doing this:

Oct 2nd to 9th Tokyo. Activate 7 days Japan Rail Pass on the 9th and go to Kyoto in the morning. Spend two nights there and move midday on the 11th to Osaka. Spend 3 nights in Osaka with one day trip to Hiroshima (possibly on the 12th). Go back to Tokyo on the 14th. Depart on 16th.

Districts not to miss in Tokyo: Asakusa, Akihabara, Odaiba, Shinjuku and Shibuya are essential. Ginza not so much In my opinion unless you want to visit a more western style posh place. Also, a day trip to Kamakura & Yokohama might be good (specially for Minato Mirai area and China town). If you like amusement parks I can't recommend enough Fuji Q, so you can get the full combo of great rollercoasters with stunning views of the mountain.

In Osaka; of course Dotonbori/Shinsaibashi is great. Den-Den Town may not be as flashy as Akihabara but is good, Shinsekai and Umeda also make good visits and the aquarium is stunning.

Now, depending on what you like there's also other places which you may want to check out, for example, Ochanomizu in Tokyo if you are into music instruments or Nakano Broadway and Ghibli Museum if you are into Manga and Anime... There's many stuff you can see and do so it's up to your likes.

If you are interested in a city, Nagoya and Yokohama are other popular but less frequented destinations that aren't as far off as Hiroshima.