Poll
43%
43%
13%
Apart from Donnie Brasco, I can't think of a single movie that clashes as heavily with The Godfather, in terms of the portrayal of the mafia family system, as GoodFellas. Godfather is an old-fashioned epic, GoodFellas is basically a biopic. In any case, they're very different films and they shouldn't really be compared in such a general way.
Saying that, I'd vote for The Godfather if I had to.
The Godfather.
Goodfellas is great, and Scorsese is an infinitely more consistent director than Coppola (who's made 3/ 4 masterpieces but otherwise has actually sucked rather a lot) but Goodfellas isn't one of his best films, in my opinion. But to compare the two is trivialises both, especially as such different films, really.