The superhero fights I always found most compelling were/are: 
 
Hercules vs Thor  -  I've always wanted Hercules to win. 
Thing vs Hulk        -  I've always wanted the Thing to win. 
Superman vs SHAZAM / Captain Marvel  -  I've went back and forth on this one over the years and I really don't care whom wins these fights, as long as the losing character is treated respectfully by the writer.