B
SMG2 takes the base of the original and builds upon it from a level design perspective to make a stronger selection of stages for 3D platforming, if SMG1 is the entry that feels more playful and revels in its Mario in space angle then SMG2 is the one that focuses more directly on the levels themselves and less so on the new novelty.
This isn't a knock against the first one at all, it really depends on what sort of adventure you prefer, the first presents more of a story be it the more cutscene heavy beginning and ending or the addition of the storybook, despite the more linear style of level design some of its stages still lean on more of a SM64/Sunshine direction at points with more open spaces, collect the 5 launch star pieces and tasks like rabbit nabbing, races and numbered ring swimming.
SMG2 meanwhile soldiers further on down the obstacle laden platforming path, it starts quicker, less time spent of creating a story and more on just getting you into the game, it assumes the player to be familiar enough with the Galaxy gameplay to kick off from World 1 at a higher difficulty level than the first worlds of the original. Its powerups are stronger and more interesting to use be it Yoshi's various mechanics or the Cloud Suit.
While both are great I'll easily side with SMG2 for its greater gameplay push, it doesn't tend to dwell on the mechanics that were heavily featured in the first game like pull stars and previous powerups, each stage tends to throw in something new before moving onto the next type of obstacle. In a way you can take note of the slight differences between the two games focuses where SMG1 uses a cosmic clone as something to do a basic race against SMG2 uses conga line cosmic clones to mirror your movements and increase the challenge of a section.
SMG2 does have something of a content issue towards the end where I can't help but feel that the obligation to match the star amount of SMG1 led to a few slapdash stages like S World's slightly altered Galaxy 1 content, of course there's actually 242 stars in the end due to the green stars and grand finale galaxy and I don't think they needed to go that far either.
But in any case I find SMG2 to be more varied throughout the main game and have more engaging level design which wins out against the first game having a slightly larger pool of umm magic to work with.
