I beat the SNES version, well I mean I got past Level 9-4, a little while ago. Didn't really give me too much trouble. In fact, I ended up giving up while playing Super Mario Bros. 3 for it being too hard! I think the SNES verison is just a lot easier since you have unlimited continues from the start of each level instead of each world like the other games on All Stars.

I'm guessing this was not part of the original Famicom Disk System version though, which probably makes it a lot tougher.