Here's an update on comparing this year's El Nino -- such as it is -- to 1997-98's:
Solid lines are GISS global surface temperaure anomalies (right axis).
Dotted lines are the Nino 3.4 sea-surface temperature anomalies (left axis).
Notice that this year has, so far, been significantly warmer than 1997, even after the 1997 El Nino began. And for every month; year-to-date it's an average of 0.26°C warmer.