Definitely the original Super Mario Bros trilogy on the NES, as long as we count Mario 2 as "USA" instead of "The Lost Levels". No other trilogy ranks that high for me regarding every entry being of exceptionally high quality. I would probably choose Uncharted and the original God of War trilogy as runners up.
Other good trilogies have at least one weak link. I don't care for Bioshock 2 or Prime 2. DKC 2 and 3 are ok, but nothing special. Resident Evil 3 is kinda meh. And Zelda 2, while I personally hold it in high regards, certainly isn't up to par with the others.







