'Raiders' ALL the way.
IMO; every Indy film after 'Raiders', Indy's outfit felt like a costume. In 'Raiders', it felt like it was a part of him and that everything he wore had a purpose. Everything was dirty, dusty and it just looked more natural.
'Raiders' also had the perfect hat; wide brim, tall crown with a sharp pinch and covered in dirt. 'Crusade' had the tiniest hat of them all. And Indy wore gloves in 'Raiders' which was a great addition.
The costume in the original felt natural and just seemed like it was really something he wore to get dirty. In the sequels, it didn't quite feel like that. Not sure how to explain it.
But 'Raiders' all the way. Love the green bag with the brown strap also as opposed to the all brown look with the black strap the sequels had. And to boot, 'Crusade' had Indy in a tie for a portion of the film...not good, IMO.