I've definitely been enjoying this :D ...
I am not very good at Cousin Meteor because I am not very good with PC style controls (pointer device plus other controls). Also, on both machines where I've played this, I can't adjust my aim and do other things (move, shoot) at the same time. I bet most any mouse would do the trick, but I don't have one. If you didn't mind making the shooting somewhat easier, I'd recommend an autofire option.
My guess is Marnyrinth is supposed to be fairly casual and easy. I didn't have a hard time getting both a Par and a Perfect on each stage, not necessarily in the same attempt. I've got a feeling some players would like some more challenging stages, or tougher goals to shoot for.
As a Mario fan from way back I really like Super Nik Bro. (I really like Marnyrinth too). I really don't think it needs enemies or being able to take a hit. Introducing required collectibles in the stage right before it gets hard was good game design. And, for me, stage 5 is indeed hard, lol. I certainly haven't won without duping the race at the end (saving a collectible near the start for last). When the King (maybe not really the King?) hit the button it was not obvious to me what to do next, by the way. My first guess was a boss fight, and I tried to jump on the thing that came after me. The bonus stage is cool, and in my opinion possibly easier than stage 5.
Thanks for putting all that work into what's made for a few good hours of fun for me. :) And also, I think it's very cool that Smitty McGrotsmeat did indeed stream a game made for him.