S.M. Bros was a masterpiece, the rest... not so much.
I was a massive fan of the first Super Mario Bros, it was simply amazing at the time, it brought so many new things, mechanics, gameplay, game elements, etc to the genre and video games in general that it is impossible to explain to someone who did not live on the 80's.
I played it so much at the arcades I could have bought my own arcade machine, If I close my eyes any time to this day I can still listen the tune of stages 1-1 and 1-2 playing in my head.
By the time the 2nd and 3rd S.M Bros came it felt nothing like the original and no sequel ever captured back my attention.
Some games are just "Good enough" and should be left alone, another example coming to mind is Minecraft, it was much more engaging when it was simpler around v1.5 - v1.7