That's a bit heretical if you consider the context in which SMB2 came into being. It introduced many new concepts not present in the first SMB and stands on its own. It isn't just another side-scrolling platform, it was also way more vertical, way more scene transitions within a single level, the ability to move context between intra-level scenes, multiple playable characters, each with different abilities. It certainly influenced future SMB games (SMB3 implemented a similar-if-you-squint slot machine mechanic at level end). Similar to Zelda 2: The Adventure of Link which was also dramatically different from the first Zelda and it too influenced future Zelda games.