By percentage? Toejam & Earl.
Toejam & Earl (Gen), Toejam & Earl: Panic on Funkatron (Gen), Toejam & Earl III: Mission to Earth (Xbox)
By raw volume? Splinter Cell.
Splinter Cell (GC), Splinter Cell (Xbox), Splinter Cell: Chaos Theory (GC), Splinter Cell: Chaos Theory (PC), Splinter Cell: Double Agent (360), Splinter Cell: Double Agent (PS2)