My four year old plays with me sometimes. He's no master, but he gets it and can navigate just fine.
Depends how good his on-screen recognition is in your opinion. If he is already good at navigating 3D space in video games, he would probably get it. The battle arena would be a good place to start to get used to the controls. If in doubt, you can always try to borrow it from someone to try out first. I don't think video stores are renting this game though. :(
My 5 year old and I play this together nightly, we run through a level or two depending on how much time we have before dinner. He's even stepped up from his usually wiimote games to a big boy ps3 controller and had virtually no problems. If there's a part where he is getting owned and churning through all our skylanders I usually have him sit out while I bust through it. This has only happened on one or two boss fights and one part with a lot of bounce pads. He hasn't gotten mad about it and understands he just needs to get better hand eye coordination before he can handle it. I would really suggest that the young ones play ranged only, and in fact Trigger Happy seems to be his favorite so this works out well.
This game alternates between pretty easy levels, and a few fairly hard (for an adult gamer of average skills) boss fights. Offhand I'd say your kid can do most of the basic levels, if you will can help him through some tough spots. Also, he might have a blast fighting in the arena with his friends. It's worth a purchase. Fair warning, you are likely to spend a bundle on figures.
I decided to get this for my sons 5 year old Birthday, on 1/2, and he loves it. He has been able to navigate the game on his own once I showed him the initial click on this it does this tutorial. He has managed to get through a lot of the game on his own. Most of the game is narrated, but there are some areas where you will have to read to him, enemies and purchasing upgraded abilities. His hardest part of the game are the heroic challenges and figuring out the strategy on some of the boss fights.
It is a great game that I enjoy playing with him together as it can satisfy both our gaming needs. The one drawback is the lack of additional characters in the stores right now.
Me and my 4 year old brother play this game a lot, and although I don't have an adult opinion I hope you take this seriously. My brother has very little game experience, he has a Leapster and plays that, but he gets the game just fine. I really do think he has to have someone playing with him for him to enjoy it, but with some guidance he can finish the level just fine. So if you plan to spend time playing with your son, or if he has siblings that would play with him, yes this game is a great idea.
The controls are not complex at all, basically just different attack buttons. Your kid should do just fine. Also, remember that you can play it with him, which would help him if he is having any pathfinding issues. My six year old loves it, and he could play assassins creed when he was four, so little kids are capable of picking this stuff up. Skylanders is alot easier than the lego games in my opinion.