In this series of articles we'll write about one or more Mario games per day, each representing a different year as part of our Super Mario 30th Anniversary celebrations.

Nintendo has some rules that it follows with its games and franchises, particularly in terms of frequency. There's one Super Smash Bros. game on each home console, one Mario Kart, and one 3D Mario. Well, rules are there to be broken.

We've previously written about how Super Mario Galaxy wowed Wii gamers, even if it couldn't compete commercially with the 2D Mario that would follow. It was the 3D Mario of the Wii generation, so there was surprise and delight when Nintendo revealed Super Mario Galaxy 2. It wasn't unheard of for Nintendo to do this - as highlighted in this Iwata Asks The Legend of Zelda: Majora's Mask was a sequel that utilised the innovation and hard work that had gone into producing The Legend of Zelda: Ocarina of Time.

As you can see in the following excerpt from that interview, it was the original intention for this game to actually be an expansion as opposed to a sequel, yet it went further than expected in development.

Iwata: So development of Super Mario Galaxy 2 began with using the first game's environments exactly as they were.

Not 2, but 1.5. So you wouldn't get too carried away.

Miyamoto: Right. We began with the intention of making a game labelled 1.5, but the development staff members were saying things like "It would be fun if we had more environments like this" and "Let's put in more new stuff." It was like "More, more, more!" and new environments started multiplying rapidly. The next thing I knew, more than 90% of the courses were new and I couldn't tell where we had kept anything from the previous game!

Iwata: So in the end, it became 2 rather than 1.5.

Miyamoto: That's right.

There were certainly plenty of new level ideas in this sequel, along with a World-based layout - or Galaxy-based, actually - and some new transformations such as the fluffy Cloud Mario. The big-ticket inclusion was Yoshi, of course, who featured in specific stages with the ability to swallow enemies and spit them out as projectiles. Other capabilities included swinging on pegs with its tongue and also dashing at high speed through certain levels.

Overall this sequel combined new ideas with a slightly higher level of challenge, with the last level being a true test of a platformer player's mettle. The two player co-op was also beefed up slightly, with the Wii Remote pointing second player controller a Luma also able to attack enemies directly and drag items to Mario (or Luigi).

Arriving later in the Wii lifespan, arguably when it was already fading in popularity, Super Mario Galaxy 2 was a commercial success without matching the unit sales of the original. It was critically acclaimed, with the debate being ongoing whether it was an improvement on the original, merely an iteration or even not up to the level of its predecessor.

That debate will rumble on through the ages - this author is firmly in the camp of regarding it as a sequel that is an improvement over the original, so feel free to heartily disagree in the comments. Wherever you stand, ultimately, this is still an essential play on the Wii and a wonderful Mario game; it's available on the Wii U eShop, too.