Jak II is a super fun game with a cool story, fun missions, and plenty of mini-games and secrets to keep you going.
Jak II starts out in the land where Jak & Daxter: The Precursor Legacy (the first game in the series) takes place. Jak, Daxter, Kira, and Samos are unexpectedly warped into the future when the leader of the Metal Heads appears through the time gate. Now in the future, Daxter escapes the Krimzon Guards while Jak is arrested and captured by Baron Praxis, the ruler of Haven City who is fighting with the Metal Heads to stay in power. Years later, Jak breaks free with the strange Dark Jak powers he discovers when Daxter comes to his rescue and the story goes on from there.
While playing the game, you may notice it's similar to Grand Theft Auto where you can drive around and explore a massive city, get chased by the cops (or in this case, the Krimzon Guards), and do missions to finish the storyline. However it's more simple. For example you don't use money to buy things like clothes, food, paint jobs, etc. Even though there may not be as much, it proves to be a very enjoyable game. And hey, sometimes simple is good.
You are given the huge Haven City to roam freely in once you get enough Security Passes to enter certain sections of the city, which will come to you as you progress in the story and complete more missions. Throughout the city will be the citizens which, if you really feel like you have to, you can kill. Also, the Krimzon Guards will be walking around for you to try and mess with, but if you do, unlike the normal citizens, you WILL be chased by them and hunted down until you're killed one way or another or you find a clever hiding spot where they can't find you for about thirty seconds. You can also steal people's cruisers (flying cars) to get around the city faster or take a nice hover around with your Jet Board you acquire later in the game. There will also be times where you must venture outside Haven City to complete certain missions and tasks.
Dark Jak is power you gain in one of the beginning missions and let's you learn new moves for it as you bring the Oracle more Metal Head skull gems. Some of the moves are Dark Bomb (a bomb-type move that effects all enemies/people/vehicles within it's range) and Dark Blast (which does pretty much the same as Dark Bomb, except you spin in the air) The rest is for you to find out and go crazy with.
Jak soon joins the Underground (a group that is working to overthrow the Baron) in order to get home, find his friends, and get back at the Baron. The missions in Jak II are fun while they are also challenging as you get further down the list. You will also notice some re-occurring missions with harder difficulties. Examples may be an escort mission, picking up Underground members and dropping them off, taking care of some Metal Heads, retrieving items, shooting down Krimzon Guards and their forces, and doing jobs for other characters you meet along the way. There are only a few bosses, but they they are very challenging.
This game has a bunch of mini-games and side tasks as you progress through your missions. You don't always have to work on the story. You can roam around Haven City almost whenever you like. You'll come across these things that can give you special challenges like looking for Precursor Orbs and racing people through the streets, to name only a couple. As you keep playing, up to four guns and gun upgrades will become available (Scatter gun, Blaster, Vulcan Fury, and the Peacemaker) which you can use to help you kill enemies and take for spins on the gun courses. There is a Jet Board challenge and stadium racing challenges. All of which will earn you Precursor Orbs to unlock secrets and cheats, that is if you don't find them lying around in areas outside of the city.
Jak II is pretty glitchy at times and that can sometimes screw you up in the weirdest ways to ways that are understandable but can still made you mad. The graphics are good and smooth which makes everything easy to understand what's there before your eyes (but hey, I'm not a graphics expert). There may be times where the game seems a little too hard, but you can always take a break, do other things in the game, and come back to whatever is giving you a hard time. You might spend roughly 15-20 hours playing this game, but it 's not too hard to get enough out of it so it doesn't seem too terribly short. If it's not one of the best games out there, I will say it is one of the best and funnest PS2 and/or 3D Platformer games in the game world and is most definitely worth a shot.