That guitar track sounds like it's EQ'ed like a french horn. It's all mid and the highs and lows seem nonexistant. I'd scoop the mids and try bringing in some highs around 10-12K. If it still doesn't sound good, it's the way it was recorded and needs to be re-done.
---------- Post added at 03:06 PM ---------- Previous post was at 03:04 PM ----------
Oh just noticed you're not using real guitars whatsoever. This is completely why. Nothing except a real guitar miked properly through an amplifier cabinet will sound good.