I'd like to start and finish this review by saying: "This game is amazing, go play it" But, since this is a review, allow me to explain a bit of this masterpiece of a game. Also, despite having only a little over 100 hours on Steam I have played this game on my older computer as the non-Steam version.
Firstly, the story is superb. If you like games with a deep plot you'll love Mabinogi, as of writing there are 16 mainstream generations. The generations are pretty long. In fact, Mabinogi is a pretty long game, don't think you'll be beating the game in a week or two, this is a game that takes quite a bit of dedication. However, not once did I find myself without something to do or bored, and as mentioned, I found the story incredibly interesting and immersive. (there are even some feels ;_;).
Secondly, the music. My god the music. Is. Amazing. I still find myself listening to the music in this game, it's great, it really, really, is. Out of every single game I've played, which, is many, many, games, Mabinogi's music is my favorite. If you like listening to the music of a game you should already be downloading this. Aside from the music already in the game, the Bard class allows you to use your favorite songs in the game through the use of MML.
Now for the gameplay. admittedly, the game is pretty old, and it shows, the graphics can be a turn off at first but you'll get used to them eventually, in fact, if you like anime/manga you may even like the game's graphics right away. There are currently 18 talents you can choose from, each offers a different style of play. Now, what really sets Mabinogi apart from other MMOs is its Rebirthing system and combat, but we'll get to that later. The Rebirth system, in essence, allows you to reset your age, level, appearance, even your gender. As you get further in the story Rebirthing often is vital because you keep all your stats and items prior to rebirthing. So, in essence, a level 1 could be stronger than say, a level 20. Rebirthing also allows you to keep all your skills, too. So you could become an archer but still use skills from the gun talent. Moving on to the combat, which is also quite a bit different from other MMOs... The combat system requires strategy, simply button mashing will get you killed. You MUST master the counter, defence, and smash skills if you want to get anywhere in this game. Also, this game is by no means pay2win. Just thowing that out there, the only things you have to actually pay for are mounts, pets, and certain cosmetic options. But even then you still get free mounts just by playing the game.
Lastly, maybe you don't want to save the world. Maybe you just want to be a farmer, or a miner. Well, you can do that in this game. You get your own, expanding Homestead where you may place crops ore veins and other things of the sort.
tl;dr: this game is amazing, go play it.