First off, the series of games is a great mix of plat-forming, three person shooting, and arcade like game play. Each game is especially difficult, but is balanced my more forgiving checkpoint system than I've seen in any other plat-forming game.
The first game doesn't have a tutorial, but starts off rather easy and gives you a chance to learn your moves.
Weapons and use of Dark Eco are introduced in the second game along with a totally new overworld and a deeper interest in story than the previous
The 3rd game farther adds upon these abilities with newer weapons and use of Dark and Light Eco in the game, this consistent improvement is what makes the game series as a whole so great.
My only problem with the game is near the end of all three games, the checkpoint system begins to become rather faulty, having you replay 5-10 minutes of gameplay, and in bosses or other special events, you start from the beginning regardless of how far you got, this is also a problem in some missions (the sewer missions) in Jak 2 and 3, and upon restart you do NOT regain ammo or magical ability.
That being said, I wouldn't let children play this game, not Jak 2 and 3, it has adult language and the game itself can be really annoying, perhaps more mature people with a little more patience, as all 3 games or long, filled with side content and unlockables.
A personal problem of mine (which does not affect my score) is Jak's change in character from Jak 1 to Jak 2, even though clearly explained and reasonable, it did disconnect me from the character a bit. I love Daxter though. Also the Desert overworld in Jak 3 can be REALLY annoying, because of the physics engine in this game, but is still enjoyable.
This game does follow a more realistic set of physics in my opinion, so the switch from something like mario, sonic to something like this will be difficult, but very interesting if you're gamer looking for new experiences.