Like I stated, Seiko makes perhaps 300 or 400K watches annually and most of them are relatively cheap quartz. So, I meant to say that the most of those USD20 or USD100 watches are not worthy to discuss here among watch nuts like us.
More to your point - I honestly don't get what you don't get. GS are mostly SS, very accurate, service is superb as the top of the line of Seiko. GS concept is the highest quality as the practical watches - I repeat, practical watches. So, no or little bell and whistles (of course there are some, some chronograph and such). The price is reasonable (I don't know the pricing for EUR or US, but GS price ranges from 3K to 7K, about) and it serves the purpose - being practical. For that, I agree that it is superb. Credor is different under different concept, by the way. Credor also is the top of the line, but more on the luxury side with Urushi dial, Noritake dial, etc., for example. It really comes down to one's expectation from the watches. As you know, my watches are not only Seikos, but variety of watches and I like and respect Seiko, GS or Credor, as much as I do ALS, Moser, Patek, etc.