They all offer something different. I see xbox 360 as the main multiplayer system, however it also has a wide variety of SP games, so my opinion would be to get the 360.
I have been using a super cheap logitech mouse and was considering getting a newer expensive mouse. All this information was great, now I know what to expect and how to help it.
To be honest, the Wii U does not interest me in the slightest. If anything I would get it for family fun, but I can just emulate a GameCube or a Wii on my PC.
Honestly the difficulty level of SP games are just stupid. Also it is very difficult to find a interesting story that is not over done. Lastly combat needs to be improved from the normal.
RTS, I know there is a lot out there but the only ones I see people playing are starcraft. The other ones are generally dead and you can play single player or with friends.