Ah, so there's this guy who sells his soul to the Devil and ends up riding around on a motorbike with a flaming skull for a head, you say? Sounds a bit daft, no? Apparently not to Nicolas Cage who had been hell-bent (*snigger*) on portraying one of Marvel's more conceptually challenged heroes for quite some time. It is inherent in the basic idea that it rides a thin line between brooding gravitas (souls, damnation, judgement, all that jazz) and all-out silliness (...he's a flaming-skulled dude on a bike...).
Given the duality, it's no wonder that the movie ends up being a bit half-assed in both ways. It has some fun at its own expense, but plays it disturbingly straight at other moments and doesn't quite get away with it. And when a movie goes out of its way to create a mythology for itself, then it confuses and irritates when the established rules go out the window when they don't suit the screenplay later on. There are several moments where you go 'Hey, but if this character could do thís, then why not thát?' The ending especially does not make much sense.
There are some great visuals though and the flaming Ghost Rider persona impresses a lot more than his Nicolas Cage alter ego, sporting a seriously bad haircut. Some good one-liners almost make up for bad writing in other places and the whole thing is amusing enough in a cheesy sort of way. A sequel seems likely, and as long as they tighten up the script along with their internal logic and give Cage a better haircut, then it might be worth a second outing.