Turbo and Overdrive were the worst, IMO. They didn't do a very good job of justifying the change from Zeo to Turbo, and ... yeah. Justin was trying waaaay too hard to appeal to the target audience.

As for Overdrive ... I really liked Gogo Sentai Boukenger, but PR's version of it was a disappointment on just about every possible level. "Once a Ranger" was okay, though it left me with a question: if the Sentinel Knight could restore the previous Rangers' powers for the purpose of the teamup, why couldn't he just do that to the Overdrive Rangers and save the former Rangers the trip? Plus ... Mack's a freaking robot? Where did that come from?

I was thinking the other day about maybe starting an RPG (either here or on HenshinTalk) about a version of OO that involves TJ Johnson (from Turbo and In Space) being hired by a private organization to train and lead a Ranger team for the purpose of recovering a series of artifacts before they fall into the hands of various monsters. TJ would be the Red Ranger, the rest of the cast would be new characters ... and whether this would be an improvement over the actual OO would remain to be seen. But I doubt it would turn out any worse.