Let's see if I can help clear up the numbers you have, though it's not going to affect it by much, percentage-wise.
My count for official North American NES releases is 677, like the number you have.
There are five compilations of individually-released games. These should be:
Donkey Kong Classics which includes Donkey Kong and Donkey Kong Jr. (is this the extra game that you think you have?)
Sesame Street ABC & 123
Super Mario Bros. / Duck Hunt
Super Mario Bros. / Duck Hunt / World Class Track Meet
Super Spike V'Ball / Nintendo World Cup
Not to be confused with compilations of games that were never released on their own, that is, Back To The Future: Part II & III and Short Order / Eggsplode! (And if you've seen Super Mario Bros. / Tetris / Nintendo World Cup, that's a European release, not a North American one.)
For curiosity's sake if anyone else wants to know what the count includes, be aware of these other tricky ones:
-There are two Indiana Jones And The Last Crusades. One is by Taito and one is by Ubi Soft, and they are vastly different games. Doesn't help much that the box art is of the exact same photo still from the movie where Indiana Jones is pointing a gun while riding a horse, but is zoomed in closer on the Taito one.
-There are two official Pac-Mans. I recall reading that there actually is a faint colour difference between the two. One is published by Namco and one is by Tengen. "But Jon," you may say, "Tengen games don't count." That's actually not quite correct. There are three Tengen games released in both the official standard cartridge but also in the black, upside-down label Tengen style. Aside from Pac-Man, the other two are Gauntlet and R.B.I. Baseball, so these officially count. Do not confuse the Pac-Man situation with Tetris, where there is a Nintendo release and a Tengen release, since the Tengen one never got Nintendo's blessing (though some people prefer the Tengen version because it actually has a two-payer mode).
-I'm counting Mike Tyson's Punch-Out!! and Punch-Out!! as separate games.
-I'm counting World Class Track Meet and the incredibly rare Stadium Events as separate games.
-There are numerous variants of boxes/covers, many of them subtle, like the "Bros." on the cover for Super Mario Bros. 3 being moved from the left to more to the right, though these are subtle and unannounced changes. Some rereleases are distinct, like with The Legend Of Zelda, but the biggest change is Metroid, where the pixel art is entirely replaced by an image of Samus (actually from Metroid II, considering the orange Varia Suit with the bulky shoulder pads). While a collector of actual cartridges might like all variants, this is still just one game.
My count for official North America Super NES releases is 718, but this number can be 720 or 721, if we're really talking about NTSC releases for the "Americas".
Again, there are some compilations.
Super Mario All-Stars + Super Mario World is quite the package, too bad it didn't come in an official box since it was a pack-in. Super Mario All-Stars is already a compilation, but of remade NES games, just like Ninja Gaiden Trilogy (though the sound got worse), and in a way, Tetris & Dr. Mario, though that one also has a "Mixed Mode" which mashes them together too, so it's more than a strict rerelease compilation.
Exertainment Mountain Bike Rally / Speed Racer - these are two games for the Exertainment exercise bike peripheral, which came separate but also together. These three carts are quite rare, along with Cannondale Cup - of which Mountain Bike Rally is a reskin of, if I'm not mistaken. Confusing enough? (Is this a compilation you didn't count?)
Speaking of reskins,
Chavez is a reskin of Riddick Bowe Boxing, and
Chavez II is a reskin of Boxing Legends Of The Ring. Sometimes the Chavez games aren't counted not just because they are reskins, but because they are sold to a limited market, supposedly the southwest US and Mexico. That brings us to 720 if you count them (I personally would).
Super Copa is a reskin of Tony Meola's Sidekicks Soccer and was only released in Brazil and perhaps elsewhere in Latin America. Counting this brings this to 721 (but when I made a poster of all the game covers, which you can see in some of my YouTube videos, I deliberately left this one out, because 720 is a much easier number to work with).
(I've sometimes pointed out the incredible coincidence that the number of Super NES games equal the number of Pokémon up to the sixth generation. It seems there's 718 at first, but then when you look further and find these three games from down south or the three mythical Pokémon, the actual number is 721. Furthering the coincidence, the Super NES added X and Y face buttons, and the Pokémon sixth generation is, you guessed it - Pokémon X & Y.)
Thank you for working out the math, FlyingArmor! Wow! It's certainly interesting, and cool to have my assumptions mathematically confirmed. Seeing that we're a tiny bit less than 2/5ths of the way through the NES and a tiny bit more than 1/5th of the way through the Super NES (if we're only counting the complete games) - or an average of a (kind-of-neat) 29.99% or just under 3/10ths done. Counting partially complete games adds a bit, but not a whole lot since the number of complete games is multiple times more than the incomplete (which surprised me for some reason - I mean, I know we have more complete games than incomplete games, just didn't think it was multiple times more).
