Perhaps coming somewhere near the top of lists that could be titled Defining series of the PS2 era as much as Forgotten games of the PS2 era Onimusha Warlords, the first game in a series of 6 was one of the big early releases of the PS2 and has recently been given the remastered treatment on the PS4.
Source: N4G PC Talking Games: Onimusha Remastered