I think you've misinterpreted 8-bit music as being easy to make...
I don't specialize in the genre, but I've heard several tracks, and understand it's core elements.
First off, already what I said, it has more layers, more stuff going on, and more fx. Especially some drums are always good...
w/e, just listen to your favourite 8-bit tunes, and try to replicate their sound. These pieces to me sound like you just loaded in 2 synths and then put in some sort of melody.
Also, the songs have no structure.
Improve this stuff before you expect to be taken aboard game dev projects. Harsh review, but it's what you need.
(I hate rating things, so I default to no stars)
Thanks for this comment. Please check out my new work! I feel I've improved greatly!