While I agree with every single point you made, there are two reasons why SMW is superior to newer 2D Mario games.
1) SMW had much, much tighter controls. I couldn't believe how "un-Mario" the controls and response time felt on New Super Mario Bros. Wii when I first played it. It's like every level is on ice. Rapid consecutive jumps often don't register as well as on SMW. This is a huge offence in 2D platformers, especially when Nintendo got it right over 20 years ago.
2) This may be subjective, but SMW is more imaginative than NSMB. NSMB feels like a revisit to old themes, whereas SMW felt newer at the time and had more creative levels. I'd like Nintendo to make a 2D Mario with the same kind of "freshness" SMW had. Again, this is highly subjective.
