So far, I've only taken down the Samedi and am halfway through tearing up the Ronin, but I haven't seen anything I'd really want to replay. And I'm definitely not a fan of the whole "Respect = Access to missions" mechanic, mostly because I'm not enjoying most of the diversions. It usually ends up with me just doing a bunch of drive-bys until I can do a few missions, then rinse and repeat.
SR2 had a more enjoyable story and replay value imo. Third was flashy, fun but just flashy.
Currently working on Saints Row 2, which isn't nearly as good as The Third.
On the other hand, the complete lack of seriousness most of SRTT has just really endeared it to me. I played through the DLC with the clones several times just because it was so entertaining.