It sounds like you imported the MIDI into FLStudio and applied some plugins. Generally, I'd be sure to do a little more fine tuning with it than just that. These files were made to sound good as MIDIs, and just slapping on a plugin may not help, but rather hinder it. I know good-quality VSTis can be be expensive, but before you go out and blow 1000s of $ on those, I'd spend a little more time with sequencers and get to know their odds and ends.
As for the music...
The Last Battle theme was pretty distorted. Really gotta watch your volume levels here, man. Plus, I'm not sure if you applied the cutoff ending in order for it to loop, but I still felt something was lacking there. I tried playing it in RMXP, and the switch from blazing guitars to quiet strings seemed too abrupt.
The Theme01 was much better, but felt a little empty. I agree with Gulch about the drums, and I think you may want to add some more bass on this one.
Though FL Slayer might be a decent guitar plugin, there are much better ones out there and I suggest you either check those out or work with Slayer until you can really utilize it well. Don't get the wrong impression from me, I think these are great - for a start. But I'd spend a little bit more time with sequencers and plugins until you can get some real high-quality stuff. Remember, that doesn't mean getting uber-expensive sample libraries, (even those can sound crappy without any additional work) but working on the actual content of songs rather than just throwing on some plugins and praying it will come out sounding half-decent.
Again, don't take this the wrong way...I just think you should spend some more time honing your skills with these programs before you submit your works to the world.
