On the contrary, there is one Jazz Jackrabbit 2 OCRemix that I know called Jazz Castle Adventure.
I like this source, I've tried remixing it before. Well, here's what I could hear:
The initial bass is too loud. There's also some unnecessary delay. Try not to stick to what the original does.
The snare is weak; try layering some snares that add up to the all the characteristics of a strong snare: low end punch and high end snap. Same with the kick. You need low end punch and high end thwip.
Not much happens until 0:41. See if you can have something there that progresses to build it up.
The 3o3 arpeggio that comes in at 1:18 has an envelope that isn't having an intense enough effect on it, so it feels like too long of a sustain between notes. The decay of the envelope creates the main sound of the 3o3 (the "eoh" sound of it), and the envelope mix (the extent to which the 3o3 is low-passed during each note) is too little. Because of that, it sounds louder than it might actually be, and it's distracting.
You should also see if you can find new leads. Right now, the brass-like leads you have are pretty static and not more meant for backup or something. Try doing some research on sync leads, and see if that gives you an idea.
The mix as a whole also sounds really close to the original; see if you can write it without an imported MIDI.
Not too bad so far, keep it up!