I think the series are ...
... initials of country capitals. The ordering refers to the country, not the capital. My guesses for the criteria are below. Unfortunately, even if the series looks good in principle, there is at least one inconsistency in all of them, so my guesses might be well of.
1) O, W, B, B, C, N, B, ?
Countries in the Americas, ordered by area:
Ottawa (Canada)
Washington DC (USA)
Brasília (Brazil)
Buenos Aires (Argentina)
Ciudad de México (Mexico)
Lima (Peru) [should be N?]
Bogota (Colombia)
Next: La Paz or Sucre (Bolivia)
[This seems to be a good fit, even with the stretch of calling Mexico City by its Spanish name. But unfortunately, Lima doesn't fit.]
2) N, C, A, P, B, L, D, ?
Island countries by area:
Nuuk (Greenland)
Canberra (Australia)
Antananarivo (Madagascar)
Port Moresby (Papua New Guinea)
B ?
London (UK)
Dublin (Ireland)
Next: Colombo (Sri Lanka)
[I'm not quite sure about this. The first ones look promising, but what about Indonesia, New Zealand, Japan, the Phillipines? Maybe only countries with a clear main island count? But then, what about Iceland and Cuba?]
3) B, N, J, B, I, A, D, ?
Countries in Asia, ordered by population:
Beijing (China)
New Delhi (India)
Jakarta (Indonesia)
B ?
Islamabad (Pakistan)
A ?
Dhaka (Bangladesh)
Next: Tokyo (Japan)
[Not quite sure here either. The first three seem to fit, but it's really patchy atre that.]
4) W, B, T, L, P, N, R, ?
Countries of the world by Gross Domestic Product
Washington (USA)
Beijing (China)
Tokyo (Japan)
London (United Kingdom)
Paris (France)
New Delhi (India)
Rome (Italy)
Next: Brasília (Brasil)
[Note: If this is right, Berlin, Germany is missing and should be in the fourth place.]
5) T, N, L, P, C, O, L, ?
[No idea here.]
Finally:
There's an enigmatic-puzzle tag here. I don't know whether there's more to the puzzle than finding ouzt whet the sequences are. I guess the tag is just misapplied, as it so often is.