As far as I'm aware, there are no microcontrollers with an embedded ADC module capable of 500MS/s @ 10-bits, at least none I've come across.
The NXP LPC4370 with a 80MS/s @ 12-bits is the highest speed ADC offered as an embedded module on microcontroller is the fastest I've come across.
You will most likely need to incorporate a external ADC with those specifications and select an appropriate ARM which can drive it.
Most ADCs with those sampling rates above 200MS/s utilize the LVDS or LVPECL interface, are 8-bit or 12-bit and are a BGA package variant, they also tend to be in the $100 to $200 USD range for 1k quantities. However, there are a few with the SPI interface, 10-bit and a Quad package variant.
You might take a look at the Texas Instruments website, they seem to offer one of the larger selections of high speed ADCs.
BigDog