No such thing, technology gets better and even games that feel perfect today would be better with newer UI, smoother framerates, or better controls.
Of course you can say that the original Super Mario Brothers needs to exist still so people could keep working on speed runs, or just cause of the history, but a better SMB with new controls and smoother gameplay should always be on the table.
I mean, the original SMB quadrilogy was one of the first remasters ever (they messed up the brick breaking physics in SMB1/LL though, so I prefer the original or a fixed ROM hack of All Stars for those.)