The following are some highlights of Super Mario Galaxy 2 (SMG2).
Co-Star
Many games in the last generation have innovated with co-op design. Not many have opted for subsidiary co-op roles. Jet Force Gemini, Sin and Punishment, Zelda: Wind Waker, and Super Mario Galaxy all have co-op options where the 2nd player controls an on screen cursor. These cursors don't feature the core mechanics player 1 has. SMG2 tweaks SMG's co-op co-star design.
The co-star player can no longer make Mario JUMP, which is a good change from SMG. Now, all of Mario's moves are for player 1 preventing player 2 from being a "bad buddy" by intentionally putting Mario into danger with improperly timed jumps. To give player 2 more of a significant role in the cooperative experience, SPIN and GRAB mechanics were added. Now co-star players can grab coins (yellow/purple), Life Mushrooms, and 1-Up Mushrooms and hand them off to Mario (player 1). The SPIN mechanic gives player 2 the ability to attack enemies, smash crystals, and grab checkpoint flags. Couple these new abilities with the old abilities to SHOOT star bits and stop enemies/objects, and player 2 can be a very helpful and active part of the experience.
The changes in the co-star design make playing as player 2 more of a rail shooter or light gun type gaming experience because there's generally more to interact with. Sit in the passenger seat of a skilled Mario player, and you'll have a considerable challenge keeping up with the action as targets move in and out of view. Because the camera follows Mario's motions only, being aware of how player 1 will move through the level can give player 2 an advantage in planning strategies.
One final element that I must mention is the sound effects the co-star can play out of either player's Wiimote. If player 1 does a good job, send them an applause sound effect. If you care to tap out sounds to the in game music, feel free. I love wiimote sounds.
2D-3D Space
I've claimed that Super Mario Galaxy is the most 3D game ever. Now Super Mario Galaxy 2 (SMG2) takes the title. Smoothly transitioning between multiple kinds of 2D/3D spaces and perspectives gives SMG2 a flexible-high-quality core that, once again, the industry should learn from. The following is a list of spatial tricks and examples.
Doing the Mario?
Everyone should "do the Mario" where appropriate (meaning learn from the design examples that great Mario games set). Some modern games have copied Mario's graphical style. Others have copied Galaxy's theme. But this time I want to focus on how Super Mario Galaxy 2 emulates design elements and gameplay styles from other games. The following are some interesting examples I noticed. Some are more fitting than others.
Super Mario Galaxy 2 is fantastic. My experience with the game was so enjoyable, it took me this long to write something about it. There's more to say about every feature of this game, but the game speaks well for itself. I plan on analyzing the bosses in SMG2 soon. Play it if you haven't already. Listen to the soundtrack for some of the best music of the year. And marvel that there were so many things that Nintendo improved from Galaxy 1.
The one thing that would really make the Super Mario Galaxy games significantly better is 3D stereoscopic visuals. I had a difficult time beating Stone Cyclone Galaxy because it was hard to interpret distances on a flat screen. Even if you don't see the interactive benefits stereoscopic graphics would add to the game, just imagine JUMPing through space that's "deeper" than ever.