There's quite a bit of fuzzy sound in all 3 songs. I expect it's just poor sample quality. What programs are you using? If I were you, I'd use Open Modplug Tracker, if you aren't already. It's free, simple to use, and more than powerful enough for video game music. It has the option to export as wav, and if you want you can always use Audacity to save the wav as mp3 or ogg vorbis. Back in the day, I used mod tracking to make all of my video game music and it was really easy. But you'd still need better sound samples. The main problem is that free sound samples found on the internet often suck, as they usually have a ton of background noise. But you can get rid of most background noise by using Audacity's noise removal, which is surprisingly effective.
Your songs are pretty minimal so far, but they are a good start. They all sound very intro-like to me, and, as intros, they are good. You just need some clean sound samples without all that background noise. You should try to make a full song. The area I used to struggle in with music was making a long song without too much repetitiveness. It's also good to have a lead instrument that stands out properly as a lead should, otherwise the whole song will generally blend together and seem like it goes nowhere. Basically having no lead can easily make a song bland and boring.
As far as music theory goes: It does take a bit of learning before it really starts to pay off, but knowing the basics can really help you understand what you are doing. However, I've known a lot of people to make awesome music without knowing any music theory whatsoever. They just used their ears and fooled around until it sounded good (I don't recommend doing this for someone who is looking to get serious about music). I personally hadn't begun to learn music theory until just about a year ago, and I had made some decent vgm prior to knowing anything about music, besides "CDEFGAB". But yeah, without knowing music theory, it really depends on how good of an ear you have for music.