This has gotta be the best one out of the New series in my opinion. Game is super fun with unique boss fights and has a unique soundtrack, probably cause its the first game in the New series, I disliked that future installments just reused the same songs from Wii and remixed them. Its refreshing to go back to this soundtrack.
I was there in 2006 for the hype, but never played New Super Mario Bros. to completion until now. I'm pleasantly surprised by how well it holds up. The difficulty is a bit breezy, but the gameplay just feels really good. And while not revolutionary (and at this point, kind of old hat) it's undeniably one of the best games on the ol' Nintendo Dual Screen. Maybe not worth the commitment of a full sit-down, but a fun time for a few minutes here and there, when you're on the go.