DQ8 is one of the more under appreciated RPG hits of recent times. It's a great example of a very solid JRPG, with a fun story, good characters and locations, fun combat, really the gamut of RPG elements, all done well. It gets little love outside the RPG fans book, but its damn good stuff.
Soul Calibur, however, is a landmark hit. It's a definitive evolution in the fighting game genre and spawned a series that today ranks alongside Mortal Kombat or Street Fighter. It's huge in the history of games in general, and particularly fighting games, and it's a lasting fighting game hit.
Really hard choice, but for contributions to the industry as a whole, I choose Soul Calibur.