That's one of my faves, also ... not a big fan of Goodfellas but all the rest of them I enjoyed ... at least as far as my attention span let me. GC laughs that I've never actually seen a movie all the way through from start to finish ... he's not too far off ...
I like almost all of Marty's movies but Good fellas is his gem IMO. Casino, Bronx Tale, Gangs of New York, etc. all excellent films but if you don't like Goodfellas you may not like his other stuff either.