Castlevania: Symphony of the Night is a game that changed how the Castlevania series would play for a long time. It's the only Castlevania game I have ever completed( not 200.6% though), and probably one of the best games in the PlayStation library. I am no authority on video games, despite my love for them, so take this from the perspective of someone who plays a lot of games but knows that they aren't the best at them.
 
Story: I gave this a 7 because, while there's a lot of it, some parts could have been better. The game starts at the final part of Castlevania: Rondo of Blood( what's a rondo?), here you play as Richter Belmont, a member of the legendary Belmont clan. I won't tell you about their history because I hope to whatever deity you believe or don't believe in, that you at least know who Simon Belmont is. Anyway, you go and fight Dracula and the less damage & time you take will boost your stats when you really start the game. When you beat Count Vlad Tepes Dracula( he is Vlad the Impaler now) you have a nice scene of text to read that gives you some important information of what happened after the fight. When you start the real game, you play as Alucard, the half-man, half-vampire son of Count Dracula. Your goal is to stop Castlevania by going through the entire castle and stop whoever is in charge.

Graphics: I personally don't care about graphics, but Alucard is just gorgeous. His sprite is highly detailed and his animations are very fluid. The enemies are unique and interesting. Don't get me started on the backgrounds, they are so detailed that one room has a floating eyeball looking right at you and you probably wouldn't notice it. This game sets a perfect mood for it's areas by making sure that no two sections of the castle look alike. 

Sound: Like all Konami games, the music is nothing to ignore. Castlevania games live off of using music and level design to create an experience like none other. Unfortunately in the English version of this game, the iconic "Vampire Killer" & "Bloody Tears" themes are nowhere to be found, I personally have found other tunes in the game to become classics themselves. Most of the tracks are made of classical type music & metal. This doesn't sound like a good combo, but it works very well. A few themes genuinely made me feel nervous, which is obviously what the composers were going for. The voice acting at best, is very mediocre. The best voice actor in the game is the guy who plays Alucard and even then he speaks in a monotone voice. 
 
Depth: This game focuses more on exploration than anything, even to the point that they give you a Metroid-like map system. You can level up Alucard and collect different items and potions to boost your stats. Mixing and matching different armor and weapons make this game very interesting to play, as you can beat it with all of the worst items, or plow through enough resources to make you feel warm and safe. The castle is very big and unless you know what you're doing, you will get lost. Some parts require backtracking or leveling up in order to stand a chance against what this game throws at you. My goal was to just beat the game, which I did( my percentage was around 184-187%) using a walkthrough when I needed it. That being said, you could play through this game multiple times and still find new ways to challenge yourself.

Addictiveness: Most of what I said above applies to this section too. Not only can you play the game many ways, but when you beat it, you can start a new game and input "RICHTER" to play through the whole game as Richter Belmont. Alucard doesn't control half bad as well. He has magic and swords. You also have a cape( cloak) that you can swap out for other ones( my favorite is Josephs Cloak because you can change its color). When you beat a boss you either get a lifebar upgrade or a relic. Leveling up feels satisfying because when you do, everything freezes and Alucard glows. Getting 200.6% completion is another reason why people will come back to this game. Some parts require using a trick to leave an area to save your progress.

Difficulty: I had a hard time rating this because once you have the right items, you basically can plow through the rest of the game with little to no effort. Like I mentioned before though, is that you can make the game more challenging( or frustrating) by choosing not to use certain items. Some bosses are weak against certain weapons like if you use a holy weapon on an undead boss, you can deal more damage. Some weapons will do absolutely no damage whatsoever( I learned this the hard way), you can tell by the color of the damage counter when you attack them( red means you're hurting them and blue means you're an idiot). If you want the best ending, you need to have 196.0% completion when you beat the game, which can be very frustrating if you are a completionist( I am not).

This has hopefully been very informative and entertaining to read. Overall I would say that if you haven't at least tried it go get the demo on PlayStation Network or Xbox Live. This is something that everyone should play once in their life. It is on my personal list of "Greatest Games of All Time".