There is no one original cut. The film opened in a variety of theaters each requiring something different. Two different film types (70mm or 35mm) and three types of audio (mono, Dolby stereo (optical or magnetic)) If you saw the film back then, it's down to remembering what theater you were at, this link can help you:

http://www.fromscripttodvd.com/star_wars_a_day_long_remembered.htm

Since we into the second generation of kids to not have been around back then, the general answer is to choose the best home video version created by Lucasfilm. Because quality plays a big part in this the GOUT (despite it's shortcomings) is considered this release. This is the 2006 Bonus disc release. So track down a copy of that.

Once you've got it, then you can look into what the public has done to improve the GOUT. This would be dark_jedi's V3, he's taken the GOUT, converted to the correct aspect ratio and added on all the various audio versions.

If this version you still don't find clear enough as in visuals, then you get the 2004 DVDs and look into Harmy's DeSpecialized version. He's taken the highest version of the 2004 presentation and taken out the parts which were included in the Special Editions.

There are variations which people remember which influence which version they prefer, if there are anything specific then you'll need to let us know what they are and people can guide you to that appropriate release.