Cinematic Titanic comes the closest of the two by far in terms of quality compared to MST3K. Riff trax can be fun when they're actually making fun of a truly bad movie but their too many attempts at skewering genuinely great flicks like The Dark Knight and Raiders of the Lost Ark for instance just suck IMO.
Doesn't surprise me, since Joel Hodgson was the best writer and performer the show ever had. He's great. I'll have to try viewing those.
Riff Trax is OK, from what I've seen, but nothing spectacular.