This topic has been repeatedly touched in discussions and I believe it deserves a dedicated thread.
Just a random quote
to start things off:
Indian makers were often underestimated in their skills.
Yes, I believe pretty much all blade smiths worldwide (from pretty much all cultures and periods) are commonly underestimated for their skill, especially nowadays! Excluding contemporary artisans, the only exception which comes to mind would be Japanese swordsmiths which I'd posit get way too much of a hype, at least as a collective group compared to their colleagues from other countries!
Rather than relying on fame, stories, fads, xenophobia/xenophilia, etc., my default assumption would be that high-end blades of most cultures and most periods were remarkably close in quality regardless of materials and methods being utilized! Pretty much anything but an easy feat - apparently, bladesmithing skills were important enough though.
Granted, not all cultures had the same needs much less comparable means to produce high-end blades. Also the quality control apparently varied quite a bit. Thus, the average quality may vary more widely and the total amount of blades produced for sure.
Just to go with the Indian example: If you can forge wootz blades (possibly from more than one ingot) in a traditional forge without loosing the crystalline microstructure, your bladesmithing skills are certainly not bad (and you could also figure out an inserted edge if needed). If you can manipulate the forging to achieve pattern-welding in wootz, you also can do complex pattern-welding with laminated steel if you choose to do so. If you can obtain suitably differentially-hardened sword blades with traditional equipment, you really know what you're doing, period.
Let's try not to focus on the pros and cons of crucible steel here. Just having a look at high-end blades from different cultures, I do see more similarities in skill (as suggested by the end product) than differences: early Celts, Alamanni, Vikings, Mediveal Europe, Ottoman, Bhukara, Mughal, Hindu India, Himalaya, Shan, Aceh, Sunda, Mataram, Kayan, Tausug, Waray, Guangdong, Quing, Koto (an admittedly incomplete, biased, and very idiosyncratic enumeration just to name a very few examples!).
This is kind of a working hypothesis and I can't offer hard comparative data yet; so far my personal experience with antique, traditional blades (from especially Southeast Asia) seems to support this notion though. Feel free to counter my claims and discuss, please!
To cut to the chase, we really need hard data. What would you consider important quality indicators for (high-end) blades and how to measure them?