Certain tweaks make this game even more enjoyable than its older brother, Contra.
Flame Thrower vs. Fire Ball gun: The Fire Ball gun from Contra is not a weapon I usually am thrilled to get. Yes, it can cover a slightly wider area by coiling around as it moves forward, but it moves way too slowly. Speed is key when firing your weapons in these games, and when you can only have 3 (or 4?) rounds on the screen at a time, having a gun that fires that slowly can leave you vulnerable. Super C's Flame Thrower, on the other hand, moves at least the same speed as, if not faster than, the other weapons. It doesn't coil around to hit that extra area of screen, but who cares? Whenever it hits something, it explodes into 4 pieces that can also take out enemies, which is just as useful and looks awesome.
"The Code": Now, people are likely to disagree with me on this one, but I actually think that replacing the 30-lives cheat with a 10-lives cheat was a good idea. It turned a cheat that almost breaks the game into a helpful push that still requires you to work hard and play skillfully to beat the game. I routinely plugged in the 10-lives code when playing Super C and beat the game that way (I'm pretty sure I beat it without the code after that), but I never, ever use the 30-lives cheat when playing Contra. I used it once when I first got the game and got to stage 5 with no problem... and it wasn't fun. Contra is supposed to be hard. It's supposed to require timing and ridiculously fast thumb speed. I dunno, maybe I'm a glutton for punishment (after all, I love that TMNT level where you have to disarm the bombs), but think Konami made the right move.
Level Design: The level design in Super C is a lot more varied than in Contra, especially in the earlier levels. Contra has some cool levels, like the Jungle and Electric Zone, but overall I would have liked more variety. Whether or not you prefer the two top-down levels in Super C to the two Base levels in Contra, it's things like the earthquake sequence after you think you've already beat the Jungle level or the combination of upward/downward/side-scrolling in the later levels that make Super C's levels stand out.
All in all, I'll take either Contra or Super C over most NES games, but the small improvements Konami made to their shooter formula make Super C the game I would choose any day.