Welcome, Roboashura. I have a few constructive criticisms for you:
1) There are a lot of wrong notes. If you are determined to reconstruct the songs by ear, more power to you. Ear training is a useful skill to have. However, there are ways to get the melodies and the chord progressions for most of the CT soundtrack, including the CT Piano Book and downloading others' MIDI files.
2) More parts. Everything is too hollow right now. Think about harmonizing and adding more countermelodies, background chords, bass lines, and some percussion. You have a whole band available, and you should make full use of it! Furthermore I would encourage you to experiment, embellish and expand, rather than just arrange. This will make your compositions more fun to work on and more fun to listen to.
3) Use better quality instruments. It sounds like you are just recording MIDI output using the default patch set. If you have the RAM for it, soundfonts will make your arrangements sound quite a bit better. There are many free soundfonts available that are already MIDI-compatible, though the better ones tend to use >128 MB of RAM.
I don't want to sound like I'm discouraging you, because you've got a decent start here. And if you were already planning to do these things, then great.
If you don't mind me asking, what program(s) are you using?