Ghetsis is one of the Seven Sages, the true mastermind behind Team Plasma and the primary antagonist in Black, White, Black 2, and White 2. His primary goal is to summon either Zekrom or Reshiram for world domination and to rid of all trainers of their Pokemon.
In the television series he is voiced by Bill Rogers. In the Pokemon Generations shorts he is played by Patrick Seitz.
Bill Rogers - I have no idea what prompted this voice for such a main antagonist, but a smoker-type voice I cannot take seriously at all. The character isn't too memorable or deep, but Bill's take makes me think I'm supposed to take him as a joke.
Patrick Seitz - Like my opinion on Archie, this isn't too much of a surprising casting choice, but his performance and tone here delivers the bad guy aspect much more efficiently and with more weight.