@devilmaysigh>I guess, I may be wrong but I don't think this is a sequel like Metroid 2 is though.
You, and others, are though. It's very much a sequel and the fact that the Twinbee 3D Classic is supposed to look shinier, newer and/or better doesn't hide the fact that Twinbee Da!! is more or less the more polished game both gameplaywise and in graphics, closing in on the style that was later present in the arcade and SNES games.
Implying Twinbee 3D kind of renders this one obsolete is like saying Kirby's Dream Land 2 or the second Kid Icarus game needn't be there because of their respective NES 3D Classics.