Usually you try to use a cascoded single stage op amp for a pipelined ADC.  If there isn't enough headroom, you can use a second common-source stage but that will limit your speed.  You can also use a gain-boosted cascode to improve the gain.  These amplifiers are discussed in most analog IC books.  The simplest is probably Johns and Martin.

Carl

Hi there.
I would start using a classical 2 stages Miller Opamp.
1. the Gain-Bandwidth is well controllable: gm,in/Cc, but you must have a high current consumption budget to get 500 MHz;
2. the open loop phase response has the minimum number of extra poles/zeros others than dominant, non-dominant poles and RHP zero; in a cascode topology the high frequency poles might likely fall at frequencies close to 500 MHz (depending on the process), thus compromising the opamp's stability; watch out your feedback network, which might likely add extra poles at the frequencies of interest, in the open loop AC response, influencing then the stability;
3. the output swing is the widest available and a good linrarity can be expected;
4. a 50-60 dB DC gain can be easily accomplished, depending on the load impedance.