Honestly how many people do you think play CS and make maps?
And then how many people play NS and make maps?
That should give you some idea why the CS community is flooded with crappy maps, and horrible remake maps.
Generally speaking, isn't it easy to find quality in a larger quantity?
Also, I am not talking about custom maps, I am talking about official maps. NS doesn't allow crappy maps to go into their releases, hell you should see all of the horrible maps for NS. It is much harder to make a map for NS than it is for CS, mainly because you have to have it quite larger and take into account that its melee vs range.
I don't think much work is put into any CS map, except for the vehicles(even though the vehicles get stuck from driving them), but I've seen more work put into a crappy Warcraft 3 map than most CS maps :p. Not that hard to make a map with two spawn points, hostages, and two-three entrances to get to the hostages.
Also just because it looks like crap doesn't mean it isn't fun, I mean I loved playing the ns_siege map, even though it had like 3 textures total, too bad LB took it off because it crashed the server too much and people would change it to that map and the server would empty out
. Ninjafall, or something like that, was fun too, even though it lacked any detail at all, it was still fun to play because it was a non-traditional map.
Even if most fun maps looked pretty they would rarely go official for any serious mod, because then it ruins the atmosphere of the game. But simpler maps which all follow the same basic types of layout should be made to look much better, because if you only have to choose left or right wouldn't you want the person playing it to go "woah, this map looks awesome! I'm gonna go the way with the orange fog instead of the way with the dripping water and puddles"