There is going the distance and then going the distance and almost winning the fight.
Fres Oquendo was robbed vs Byrd and was ahead on lots of people's score cards when he got stopped late vs Ruiz - for me, Fres was (and might still be) a world class Heavyweight.
Howard Eastman lost every round vs Hopkins, it was hardly competitive - not the sign of a world class fighter. As I said, Robert Allen did better and I would actually say Allen was world class. Having said that, a case could be made for Eastman given the relative closeness of the Joppy fight and the Soliman win (oh and the closeness of the Abraham fight)... Its a debatable one.
My argument to the your post was that "going the distance" against a P4P giant and that ALONE isn't necessarily a sign of being world class. The manner of the points defeat must be taken into account. Oktay Urkal lost his first challenge to Harris on points, but the manner of his defeat meant he started as favourite in the rematch. Sam Soliman won't be as big a dog vs Winky Wright as he was prior to match 1. Both these were truly "honourable" defeats - Eastman's wasn't he lost big. Chuck Wepner was two minutes away from lasting the distance, but he still would have lost a landslide and wasn't world class.
I know what your going to next - turn it back to Gatti and his two big loses, but Gatti has world class wins on his resume. Eastman, Godoy and Wepner don't.
The British Light Middleweight contenders that you mention were never world class. Never looked like beating even the poorest of the big four world champions and never fought the callibre of opponent to even guage how they'd do at that level. Takaloo was brave vs Santos, but was outclassed essentially - similar to Eastman vs Hopkins... but Takaloo didn't have a close fight with any recent past or future world champion to say a "but" as you can with Eastman. Thats why I am frustrated they hardly fought each other in their primes.
It was different to the Light Welterweights (i.e. Hatton and Witter) and the Super Bantamweights (i.e. Oliver, Brodie and Mullings) - some of these (from both weight devisions) proved they were world class, so it would have been nice to see them battle it out with the highest accolade at stake, to generate more money. Unfortunately, it never worked out for the Super Bantams - but it might still do for Hatton and Witter.