Here is an image which shows Bill gates was the first to show a tablet like thing to the world in 2002, and no-one took notice. After that Steve Jobs showed the iPad and everyone saw it as the first tablet in 2010.
It turns out that when Balmer showed the Surface, few took note of it as a copy of the iPad. That looks like a little unfair for Microsoft.
Microsoft benefitted from a lot of things that Apple first introduced in the MAC, say the Graphical User Interface. This time though, it seems that Apple took a better note of the Tablet PC.