These are your first levels? Not bad! Your terrain/ground is pretty nicely varied all throughout the levels, a lot of fun-looking action is required by the player, and you've got a good concentration of enemies to the point where a player will be neither bored nor overwhelmed.
I don't really have anything to complain about, though if I were to nitpick anyway, I kind of get the impression that level 3 appears to have a bigger difficulty jump than I would have expected, comparing it side-by-side with the first two levels. It's not really a major issue though.
Are you planning to not use Yoshi coins or anything like that? There are a few points in these videos where it looks like you were planning to add some sort of secret (i.e. the 0:35 mark in level 2), but you don't actually seem to have anything substantial hidden other than some coins.