Hi, I have to agree with SiriusBeatz on most of what he's said, particularly timing. In places where there's repetition, which there does seem to be a lot, you could copy and paste if you have a "snap-to-grid" kind of function in mixcraft, I don't know, I use cubase.
The main thing with most of these is that it seems to be a melody with slow moving chords underneath. Something to think about would be making the chords underneath more interesting, rhythmically, instead of just holding them on for the whole bar (ALTHOUGH YOU DO HAVE A COOL MOTIF GOING ON IN THE ACCOMPANIMENT OF SECOND SONG. Do more of that kind of thing). That said, that kind of thing does seem to suit the whole villain theme thing you've got going on here, which I dig. Also, similarly, you could think about adding counter-melodies - something that may respond to the melody or answer it in some way. This may create more interest as things do seem to be chords + melody. And perhaps thinking about using more individual instruments. Correct me if i'm wrong, but it sounds like, in the orchestral songs, you are using, for example, a brass ensemble sound or string ensemble sound to play chords. This is absolutely fine but I guess in real orchestras each person would have their own "track" so to speak. It may just make it sound fuller if you have violin, viola, cello and double basses tracks instead of one string ensemble. That way, also, you might think about different accompanying phrases or counter-melodies!
I know it kind of sounds like a chore but, with orchestral writing, I think it will make it sound far more realistic and will open up the songs for you!
In terms of the last song, I think you've got a particularly tough job trying to make jazz sound good on VSTs. I mean it's definitely possibly if you're using synths etc. But sequencing real instruments in a jazz set up is never particularly convincing, at least to me. The drums in particular as jazz drumming is so "feely" for lack of a better word, programming generally does it justice. I'd say for your last song, you could have kept the hi-hat/ride cymbal going like in the intro at 0:23 where it seems to stop and just do cymbal crashes etc. That said, definitely don't give up on jazz at all when using technology, but maybe use more synthetic instruments or try to record your own authentic instruments in addition to VSTs.
OK, I'm rambling on. Basically I'd say, echoing SiriusBeatz, that timing/clarity in writing is key but also to think about separate lines