One step forward and one step back with this one. While it's clear that this game is more sophisticated than its predecessor in a few ways, a whole new set of issues appeared to fill in for the old ones. Enemy spawns were the biggest problem I had with the old one and it was partially fixed. Level design I found to be more annoying on average compared the the first game- at the very least for the first half. The last level is just as fucked up and forces you into a boss gauntlet at the end. The extra ninja upgrade is really cool, but can be really annoying when it induces extra sprite flicker. They also obscure enemies coming from behind.

All positives are about the same as what I said of the first game. I'd call it a worthy sequel but not exactly a better game.