I agree with Qui-Gon and Obi-Wan-absolutely perfect. Mace Windu is strong enough to warrant deeper stories. Other than that, nothing from the prequels save for Duel of the Fates.
Sequels to the OT would have to be far along in the EU if the original actors are used. There can be no Heir to the Empire etc. because that passed long ago. With the current shift in moviegoer taste, it might be prevelent to do a film version of the NJO. (Can't believe I said that.)