At the time of this comment, the Ark of Truth and Continuum movies are not included with Prime (but still available for purchase).

Also at the time of this comment, the original 1994 movie is not included with Prime, but is available with the HBO Channel add-on (7-day trial) here (also the Director's Cut here).

(I say "at the time of this comment" because I may not come back here to update this when the availability changes.)