You may be right when you say that the animation got even worse after the first series, but if you ask me, Adventures of SMB3 and SMW were much better than the Super Show in terms of being true to the games. (I'm not sure if the writing was any better, though, considering that "The Ugly Mermaid" is probably one of the stupidest episodes they ever did.) I mean, c'mon, the Super Show had the gang doing out-of-place movie parodies for no apparent reason! (Ironically, the episode that's just been mentioned was a "Ninja Turtles" riff.) It's enough to make me think the writers had Super Mario confused with Bugs Bunny. (In fact, the episode "Koopa Klaus" has the good guys arriving by way of burrowing and emerging from underground, similar to Bugs.)
Speaking of the Super Show, it's getting a DVD set tomorrow that features the first 24 episodes (in production order, that is). I probably won't be getting it, though, because they most likely still haven't bothered bringing the songs back to the action sequences. (And this is coming from the same company that released "Heathcliff" the way it originally aired.) Amazingly, I haven't seen a single mention of the set on this side save for this forum.