Qualifying a smart phone device as "best" is very subjective. In addition, depending upont the desired applications and use cases, best will vary from individual to individual.
In the innovative class, it's hard not to suggest the iPhone. It's a very intuitive device and possesses a host of great features. Where it may fall short for some is in the obvious areas of no 3G, dedicated QWERTY keypad, and Email.
The latest Motorola Q device has the "best" QWERTY keypad, but Microsoft applications are not necessarily the most cutting edge and that Motorola device lacks WiFi and a 3.5mm headset jack... again if that is something important to the user.
The RIM 8820 is boasting a pretty robust feature set, including WiFi, but its still an unsexy Blackberry at the end of the day.
Samsungs latest blackjack (SGH-i780) is the first Windows smartphone with a 320 x 320 resolution display, complete with touch screen capability. althought the QWERTY is a bit cramped, the device is well equipped with 3G, WiFi and Bluetooth 2.0 (not too shabby!), not to mention a touchpad for the ultimate in navigation, a 3.2mp camera, and built in GPS! If they manage to cram in a 3.5mm headset jack, this baby is certainly a contender for consideration.
This is just a brief list and you get the point as to what "best" can be. depending upon how "you" will want to use the device is what will determine "BEST"!