Devil May Cry, definitely! Something that begun as one of many RE4's demos, ended up as an inspiration for other series, such as Bayonetta!

Dark Souls: it proved that gamers are still craving challenge and created its own genre as well.

Metroid & Castlevania: without them, we wouldn't have one of the greatest genres of all time!

Onimusha: my favourite one. It's a living proof that hope dies last. We'll get another entry after 20 years! (Dawn of Dreams was released on 2006)