For personal reasons I'd have to nominate Argentina 97, because it was what turned me into a Ralf fan.
In terms of excitment/outcome there are quite a few I could nominate. Germany 2000, Magny Cours 2000 come to mind as well as Canada 2001, seeing Ralf beat his brother in a straight fight was very satisfying for me.
And, finally, of course, Jerez 97 for obvious reasons
.