I think Radiant Silvergun used the Saturn to its potential. Why? excellent high rez backgrounds, great animation and huge 3d bosses. As for 704x480 I'm not sure it was ever used as TV generally don't support that.
Of course I am a sucker for Radiant for overall use of the Saturn's awesome Titan ST-V board. I agree with Venom, but there are also games like Virtua Fighter 2 and PD Saga that are colorful and imaginitive using 3-d polygons in the crispest of ways. As for the resolution question, I have no idea.