Rhakkus was not in G5; he was killed in Bernii-Uss in G2. In fact, every Drakon was killed in G2 because they did not flee with the other Drayks and Serviles when the Shapers purged the Valley, with the sole exception of Orriss-Blaze (I most certainly misspelled that). Isss-Ta was a Drayk, not a Drakon, so that wasn't her. Not only that, a proud Drayk, so canonically she would never allow herself to be turned into a Drakon. Plus, in G4, she stated that sh came to Northforge to help reserve the Geneforge there, so there is no reason to believe that she left the facility. In fact, both of those Drakons in Inner Gazaki-Uss are probably the product of Jeff going "Meh, why not"
To answer your question; Nope. Not a single character was in all games. Amena Blade came the closest, but he was not in G5.
@Potato: Nope. He was a little tiny bit in G3, but that as only for Loyalists. And Akhari Blaze was only in G3-5.
Edit: The Great Archon