I agree with some of the points made in this thread. It is a very fun game, maybe 10 material. But I do have some minor criticisms.
1) What's with the camera? They did a pretty good job in SMG, but I'm up to 70 stars in SMG2 and I've run into at least two instances where the camera man was behind something and I couldn't adjust it to see. In fact, both times I've had the problem were in the beachbowl planet. First when I tried to go into the tower and the camera wouldn't go down so I couldn't see mario or the sign next to him pointing "up". I spent another 20 minutes looking elsewhere thinking I was in the wrong place before returning and trying again. The second time was in that watering hole on the same level, where I jumped in and couldn't see anything so I had to get back out and try again. Why is it so hard to figure out that if the rendering system doesn't have to draw the polys for the main character, then maybe the camera is in the wrong place! 3D camera tracking shouldn't be that hard. There should be an "optimal" position for the camera for any point on the screen that the character can be dependent upon which way he is facing. I shouldn't have to think about it at all. I'll grant that it is better than some other 3d platformers, but it seems like such a simple thing to do...
2) Why can't Yoshi grab coins? Somehow he can grab just about anything else in the game, but not the coins.
3) I've had some "galactic shakes", where the whole screen is trembling. I've only seen it on the boulder ball comet challenge, but definitely a bug that didn't get worked out of the system before release. Didn't interfere with gameplay, but a minor bug anyway.
4) Preference: I don't like the hubs. They are a useless waste of time. I finish a planet and get some kind of trophy for my hub that chubby makes a comment about, then I have to walk to the opposite side of the spaceship to go to the next planet. Comeon, what's with that? At least keep me at the helm if you're going to distract me.
5) I agree with the repetitive things that could be done once or twice, then ignored from that point on. I don't need to know that "a ghost has appeared" every time I use Luigi. And with the coin / star bit / commet coins - um, one screen / one acknowledgement please? I don't like pushing A, then A, then A, then A, then A again as it deluges me with useless and repetitive information. One screen giving a summary is good.
Having said that, I think this is definitely better than the original SMG, especially second player being able to do so much more. I loved NSMBW and that is better than SMG2 in my opinion. From the quick abduction of Peach to the perfect for 4 players all ages gameplay (bubble when in trouble) and super quick navigation...I yearn for the next incarnation of that one.
