As others have said, of course you can have a opinion of your experience up to this point. Just because you might haven't seen the most mind-boggling twist-ending in video game history, after the most tedious and terrible gameplay, it doesn't mean your opinion isn't valid. To fully review the game as a whole, however, you should play a basic percentage of the game and see most of its gameplay features, plot elements and assets it has to offer; just because you may detest the first one or two hours it doesn't mean it can't blow you away later on.