but you dont want a fake looking bike..even though its cgi and fake
something like that.. 
The problem is that ghost Rider's bike is as much a part of the character as cage himself. Through all of his incarinations he's always driven essentially a chopper, because he's supposed to be a "dark hero". Putting him on some fiberglassed, performance pos would be like having the Lone Ranger ride on a donkey.
This is one of the earliest pics of the modern Ghost Rider I could find:
http://splashpage.mtv.com/wp-content/uploads/2010/01/ghost-rider-elvis-jacket.jpgSee? Even from the start it was a custom chopper. Those chain trees are iconic to the design and have carried over to a lot of his incarinations. You have a TON of leeway on what type of bike you design for him, but it should always be an older looking chopper because... well that's just what he rides.
The other flaw in logic is that Ghost Rider should be doing traditional, realistic bike stunts. His bike is POSSESSED AND ON FIRE! I'm pretty sure in a couple of the comics they had him drive right up the side of a sky-scraper and in a couple of instances the bike actually flew! And they are worried about how realistic a pathetic stunt like a kick-flip will look?