I had to think hard before I answered this one.
I chose the SPEEDERBIKE CHASE in RETURN OF THE JEDI.
It is awesome!
Here you have the Skywalker twins in action, with no shields, and nothing but their skill and the Force between them and blaster bolts and giant trees whizzing by.
The prequel trilogy's best challenger was the Pod Race - especially with the extended footage on Lap 2 restored to the DVD. The maneuvers as well as the gauntlet of obstacles well outdoes Obi-Wan vs. Grievous (in spite of how cute Boga was). While it's true that the AOTC trailer shocked me when I saw Obi-Wan jump out of Padme's window so high up in a tower on Coruscant, the chase did not have as many participants as did the one on Boonta Eve.
In some respect or another, all of these chases had some shooting, but the heroes weren't testing their aiming skills like Luke does on the speederbike.
Coming into the Classic Trilogy, Han's a great pilot and the asteroid sequence was awesome from back to outmaneuvering the star destroyers. It's really hard to put this one down. However, the Falcon was running and not directly fighting back...I guess what Luke did took even more skill - with no shields.
As to the original trench run in A New Hope - they had sheilds, there wasn't as many blatant obstacles unless you use the video game as your standard, and I guess it seemed Luke had time to relax and use the Force (inspite of the fact we know he barely had any time - but R2 bought him a little with his sacrafice, as well as that of Biggs).
I guess the Speederbike Chase in ROTJ looked absolutely crazy. I didn't check how others voted before I did. In fact, I was a little surprised that ROTJ is strongly positioned to "win" this poll. But I think in the end, it deserves the accolades!
"Move closer!" "I take these two; you stay on that one!"