I loved Jak & Daxter: The Precursor Legacy to bits. It's a stunning game. Like someone else on the thread said, it's a beautiful, poetic and explorative platformer that is just fun.
However, Jak 2 is a boring, annoying and clunky mess in the gameplay department. This series did NOT need guns and vehicles, but the allure of the GTA sales were too much. I did like the plot though. And I still finished it out of stubbornness, but I was disappointed beyond belief and hoped that Naughty Dog would go back to the series roots with number 3.
It did't happen though. Jak 3 still had guns and vehicles, but it was a lot more tolerable. Took me a long time to finish it, but I eventually did. Tolerable, but still not as simply fun as the first one.
Unfortunately, and to be perfectly honest, the first game is the one I truly miss. I would love for a Jak & Daxter 4 game to happen, but only if it was along the lines of the first, else they needn't bother. Ratchet & Daxter already fills the platformer with guns void and with a movie coming out to cinemas in 2015, Insomniac is rather likely working on a new one for PS4.