I think KOTCS and DOD will always feel like slightly extended family to the original 3, just because of the prolonged time period between them and the trilogy. I don't see it as a slur on their quality, but when you have a tight trilogy made by a close knit group of people released within an 8 year span, and then get another film 19 years later, and a further film 34 years later, they're bound to feel 'apart' from those first movies, not least because the audience has either changed or grown up so much in the meantime. Watching a sequel to a film 42 years after watching the original is never going to be able to recapture the original's magic 100%, regardless of how good the sequel is.