Long term... Ratchet & Clank + Uncharted when coming down to Sony published franchises. Resistance will go beyond 2 million but right now I think COD4 is stealing its thunder.
Otherwise FIFa 08', PES 2008, COD4 & Assassin's Creed will become the first 3rd party franchises to go above 1 million some time by the end of December or at the start of next year.