World book confirms: The Greyjoys always styled themselves as "Lord Reaper of Pyke", it's a local title like "Shield of White Harbor" or something. It's not an equivalent title to "Lord Paramount".
Moreover, the way the World book phrases it, Aegon did want to appoint a new ironborn House as "Lord Paramount" of the Iron Islands.
So yes, it appears that Vickon Greyjoy and his successors were all "Lord Paramount of the Iron Islands".
- Actually I think that it is not really clear. According to the World book, Aegon wanted to appoint a new "lord paramount" instead of a new "Lord Paramount" (like in the Reach or the riverlands). So there might be the possibility that the title 'Lord Paramount of the Iron Islands' does not exist (after all there is no Lord Paramount of the Westerlands either). The Sword of the Morning (talk) 07:27, February 4, 2017 (UTC)