what do you think the best types of microcontrollers to use in control system

It's up to the function of the control1-in the past they used PIC microcontroller eg, pic16f877A but it easy to be burned and damage2-Now the arduino take a good place instead of pic especially that it's easy to be programmed and installed
3- you can use PLC eg.
Mitsubishi Siemens
4- you can use Relay for a very simple control system

it's based on the project you want and how many features you will use ..
like if you don't need PWM so why you should use MicroController with8 pins of PWM !! i prefer pic16f887A with internal Oscillator and other useful functions ...
and if i want to use USB i use pic18f2550 ..
for test and small project i use pic16f84A :)

Atmel MCU MEGA Xmega SAM

i think the atmega is the best

AVR is the best in term of technical support, while TI DSP controllers have a more computational power. 

there is no absolute best my dear , it depends on a lot of things , the process , its priority and the budget available .
for example triconex PLC is famous for emergency shutdown system (ESD) due to its triple redundancy features , but it's price won't make it suitable for a simple control operation ..
hope you get what i mean :)

i think it is PIC it's have big information support

I think it's PIC family , we can use it in most of control systems it's support alot of functions.

I think AVR family microcontrollers are the best choice for control system, because they have reduced instruction set computing, that enable for its program execution to be faster than other microcontrollers. Its mean less heat when AVR chip is working. And it is easier/more simple to be programmed.

AVR have internal EEPROM, internal ADC (analog to digital converter), in-system programming, etc.