The best is largely a matter of preference. If you set on an Android Tablet then the ASUS Transformer Prime and the Acer Iconia 510 are both great devices. They have the latest version of Android and both Acer and ASUS have a good track record of keeping their tablets updated. You also have quad-core Tegra 3 power which gives you access to the very best in Android gaming.
That being said Android specific and Tablet specific apps are limited. The iPad is always an option if for no other then that the app selection is insane.