Fake Guitars based on free soundfonts WILL always sound horrible. It's not artistic liberty to go and say "To my tastes this sounds good!" when it comes to this. Your dismissal of suggestions for alternatives and improvement from the many people who have posted in this thread is dumb, if not outright rude.
You are fooling yourself by claiming the only way you can musically improve is through better samples. Want to know how to make shit sound better for free? Get a better (FREE!) string soundfont, learn to do shit like realistic velocity editing, automating the volume, adding vibrato, working with ADSR envelopes and using the proper articulation for each need (And this is only the strings I'm talking about!). A realistic sound is not achieved by slapping a more expensive sample library on a midi track, but by knowing how to work with the stuff you already have.
As for arrangement, again, compare it to like, any remix of this song you can find out there, and you'll see how bland this is in comparison. It's time to wake up and smell the coffee, you have a shitton of things to learn before your arrangement will come anywhere near what I'd call 'good'.
Edit:
I'd also like to point out that this is a really dumb example in this case, because the Naruto OST has ALWAYS used real guitars and drums. With good reason.