No one is saying the Godfather has to be the best, but to dislike it shows a neo-hipster too-cool-for-the-room bullshit that just isn't believable. It's like hating on The Wizard of Oz. You just don't mean it.
Just rewatched it on Amazon, it's not as bad as I remembered it being. I guess I was just let down from how epic the book was. There's an amazing HBO miniseries that could be made from that source material.