Hey, programad, I listened to your song. I liked it and feel that it would work perfect for an old-school 2D platformer.
However, there are some things that could be improved. For instance; the drums used sound very unrealistic. I would try to add some velocity variations and use more realistic samples. As for the drum sequencing; it's basically the same loop over and over. I would insert some fills into the drum part to add variation. But even inserting a random snare or a random kick here and there will help add variation. Lastly with the drums; I felt that the crash cymbal was too low in volume. I would turn it up in the mix.
Mixing-wise, everything sounds like it's playing from the center. I would try to pan the hi-hats farther left and the synth pads farther right. Panning will help give each instrument its own space. Arrangement-wise; the guitar, the synth pads and the vibraphone seem to all be playing in the same range. Personally I would raise the vibraphone up an octave.
So I think the following things will improve your songs:
1. Make sure you use realistic samples.
2. Make sure you add velocity variation to the samples. This will especially help your drum parts sound more realistic.
3. Add variation to your sequenced parts; so it doesn't sound like a loop is being played throughout the whole song.
4. Pan some of your instruments; so that everything isn't playing from the center.
5. Make sure not too many instruments are playing in the same frequency range.