First of all, you must bare in mind that this is the Turkish point of view, do not expect for history accuracy. Historically, this is quite a disaster (to name a few things "MISPLACED": The Byzantine Empire was, in the 15th century, at it's lowest point, with lots of debts, it had almost nothing to do with the happy and celebrating empire that you can see in the movie. Then again, the Ottomans did plunder Constantinople for 3 days after the conquest!! So the final scene it's a big lie.)
For the average viewer it is more important the artistic value of the film, for "Fetih 1453" it's not a History/Documentary/Biography one. So, how good is it? Well, it's an average movie, with good action scenes, nice visual effects (exaggerated from time to time), a good enough script (neither excellent nor dumb) BUT, most of all, it's a strong recommendation for the fans of action movies with a distinctive fragrance of history. "Braveheart" and "Gladiator" are 2 of the masterpieces in the branch.
"Fetih 1453" has some good acting, some bad acting, some good directing (but he took an overwhelming task here with this subject - he managed enough well I could say but no cinematic breakthrough at all). So, sincerely, I would have ranked it 6 (that would be a mark that I call "only for the fans of the genre", but the movie has one ACE - the Picture, ladies and gentlemen! A beautiful job done here. Artistic indeed!
At the end, you get no essential idea about life, feelings and beliefs - as what I consider to be a purpose of all arts - but an average nice to see action movie.