Just because I wasn't impressed with the demo it doesn't mean I'll stop liking Duke Nukem. Even if the full game sucks, I'm a Duketard for life. Like any real fan would be.
What I heard about Doki Doki Challenge was that the original Super Mario Bro 2 was deemed too hard for Americans, so they took the game Doki Doki Challenge, inserted Mario and his pals, and called it Mario 2.
Did you know a lot of old Mega Man characters are named after musical items/themes/bands/etc since the original "theme" of the game was fast paced Rock and Roll?
Rock (Mega Man's name) and his sister Roll Rush his dog Beat his bird Tango his cat Blues (Proto Man's japanese name) his "brother" Bass and Treble
Also, Mario 2 was a dream, and Mario 3 was a stage play that Mario wrote about his adventures in Mario 1. Mario 1 was the only REAL adventure that Mario went on in the tri-series.
But did you beat SMW? Also, to elaborate on SMB2 a little more, Shigeru Miyamoto was actually involved with Doki Doki Panic, while he wasn't involved with the original SMB2. So while it may not have been a "mario" game originally, to Miyamoto it was likely a spiritual successor.