Caveat I'm a programmer, not a musician, but I have dabbled, and I do on occasion need to choose pieces of music (have spent this afternoon sifting through soundcloud). You sound like you have some playing skills however I will dive into criticism because I think it's how you are most likely to get to 'production quality':
Overall biggest non-professional thing was the timing - it didn't sound 'tight' enough. In the 70s you might have got away with it, but modern production standards are so high you are expected to cheat. When we don't hear bang on timing, it's either got to be deliberate, or there's 'something wrong'. Having said that piece 1 wasn't bad for timing, 2 was bad, 3 the timing wasn't so important to the piece, 4 was pretty awful.
A possible way around this if you are using live recordings, may be to make a loop in your sequencer, and record a number of takes of each section (e.g. play a 20 second section in a loop for 20 mins straight) then pick the best versions, and if necessary alter the timing manually in your audio editor / use some splicing method for this.
I would say piece 3 was the strongest to me, most likely I would use in a game (you could target the RPG audience), although I would lose the snare drum because it limits the adaptability of the piece. Piece 4 production stood out as really needing work. Piece 1 the drums was interesting although the composition not so much. Piece 2 was a no, unless you are scoring late night cheesy low budget euro police dramas.
I think to make progress you should really study some production tricks / mixing / effects / compressors etc because until you can get 'that sound' that pops, you will be unlikely to have success. That is before we even get to the music contents.
If you haven't already I would make some pieces that are entirely electronic, i.e. throw away your instruments and concentrate on learning this side. Then gradually bring the real instruments back in and consider them as producing short samples for you to integrate into your tracks. Then gradually expand the real instrument sections as you get more used to it.
Last thing to mention is the concept of 'musical space', something I never really was good at myself. When you pick up an instrument for say a guitar part .. don't play it continuously. Play it for a bit in a section, then stop, let the other instruments take over. Then come back again, ebb and flow between the different parts. This is much more interesting to listen to. And tends to be more rhythmic too, and adds drama.