I stayed in the Shinagawa Prince last year, it was my company's choice not mine, the views from the rooms are fantastic - the entire Tokyo skyline but even by Japanese standards the room was tiny. It also had about the narrowest single bed I have ever slept in! I have also stayed in Akasaka, as a tourist I would go for Shinjuku or Shibuya over Akasaka, there's nothing to see there really. One recommendation for a visit is the Tsukiji Fish Market - I know it doesn't sound like a tourist attraction but it's worth a visit. There are some weird and wonderful things on offer!