For the purposes of list, I've imposed only two rules: The games must still be fun to play today, and only games which were commercially released during the NES' heyday are considered. That means no pirates, ROM hacks, bootlegs of unreleased titles or contemporary homebrews are eligible.
But first, a few more titles that, while good, didn't quite make the list.
50. Mario Bros. (Nintendo, 1985)
The original Mario Bros. one gets a lot of flak from retro and modern gamers alike, and I'm really not sure why. Sure, it hasn't aged quite as well as the legendary sidescrolling platformers that succeeded it, but it's still a pretty entertaining game in its own right. Bump enemies, dodge fireballs and icy floors, collect coins, shove player two into that enraged shellcreeper coming for your blood... what's not to love here? It's easily among the best of the black box era games, if nothing else. Hell, it even spawned a pretty fun little two-player competitive minigame in Super Mario Bros. 3, so it must be good!
49. Arkanoid (Taito, 1986)
Another game known for its wacky plot, introducing a wireframe Moai head named "DOH" pulling Earth's space forces into a pocket dimension or some such nonsense. It's all a bit arbitrary, though, since this never comes into play until the final stage of the game; until then, it's all about smashing bricks with a ball and paddle in a game heavily inspired by Breakout. The gimmick that sets it apart, though, is its powerup system - broken bricks drop icons that enlarge your paddle's size, give you multiple balls to break bricks with, allow you to "catch" the ball and release it at a more favorable angle, and my favorite, the ability to shoot lasers from your paddle to break bricks and destroy enemies. The game even came packaged with a custom-made controller that featured an analog knob, which made the gameplay much more smooth than with a standard controller. It's a bit of a scarce collector's item these days, but if you can track one down, give it a go with this game. It will not disappoint!
48. Kid Icarus (Nintendo/TOSE, 1987)
47. Dr. Mario (Nintendo, 1988)
While I'm not a huge fan of competitive puzzle games, there's no denying that Dr. Mario has that good old addictive charm to it. There's a true sense of frantic challenge as you try to clear an entire screen of colored viruses, trying not to let your pills fall in the wrong place and create obstacles that will take a significant amount of time and effort to clear (and probably gum up your efforts even more as you do so). Hell, there was even a two-player competitive mode, which couldn't be said for Nintendo's version of Tetris. I also both praise and curse it for having one of the catchiest tunes in all of gaming; I first played this game over twenty years ago and I still have that Fever tune stuck in my head...
46. Bubble Bobble Part II (Taito, 1993)
Not to be confused with the relatively common "Rainbow Islands: The Story of Bubble Bobble II", Bubble Bobble Part 2 is one of the infamous "Taito Four", a set of four Taito-published games that were released late in the NES' lifespan in extremely limited quantities, and as a result now command outrageous prices online; it's not uncommon to see each one selling for upwards of $200. A shame in this one's case, as it's an update of Bubble Bobble with improved visuals and music and the same addictive gameplay qualities that made the original a hit. There are even boss battles added in every twenty stages and minigames that can be played to earn extra lives, giving it a slight Mario-esque feel as well. The only real letdown is the two player mode, which no longer allows for two players to take on levels simultaneously - instead you're stuck alternating turns whenever one player dies. Still, Bubble Bobble Part II is a beautiful game and very fun to play, and well worth checking out if you can get your hands on it.
45. Deja Vu: A Nightmare Comes True! (ICOM, 1990)
The second of the so-called "ICOM Trilogy" for the NES, Deja Vu was a slightly more realistic take on the point-and-click adventure genre. As an amnesiac framed for murder, it falls to you to recover your memories, clear your name and uncover the real culprits behind the crime. As with the other two games in the series, some puzzle solutions are a bit obtuse and it's possible to get stuck in an unwinnable state if you're not careful, but the solid, atmospheric soundtrack and tense narrative make it an unforgettable experience regardless. It's just a pity that Deja Vu's sequel was never released on the NES; however, it did eventually get a Game Boy Color port in late 1999.
44. Guerilla War (SNK, 1987)
Named "Guevara" in Japan and appropriately starring Che Guevara and Fidel Castro as they waged a two-man battle to liberate Cuba, SNK (quite wisely) decided to remove all real-life references when they brought the game to America in both arcade and NES form. The arcade version of the game featured a rotary joystick that allowed the player to move in one direction and fire in another at the same time, something they attempted to recreate in the first two Ikari Warriors games on NES with pretty terrible results. Thankfully, the port of Guerilla War abandons this idea and just has four-directional movement and firing, as well as considerably quicker gameplay speed. It's great, fast-paced fun, especially with two players blowing up everything in their path.
43. Uninvited (ICOM, 1991)
The second of the legendary "ICOM Trilogy" for the NES, and it's a good one alright. A horror-themed point and click adventure game that has you exploring a haunted mansion in search of your sister, it was also notable for featuring some surprisingly gruesome scenes for an NES game. The animation is minimal at best, but the well-written narrative, atmospheric music and tense, dark story kept you engrossed throughout. It all makes me glad the point-and-click adventure genre is finally getting the revival it deserves in more modern times - younger gamers really were missing out on something special.
42. Klax (Atari, 1990)
"It is the nineties and there is time for Klax!" Well, the nineties are long gone, but Klax is still around and just as fun to play as ever. A clever little tile-matching puzzle game in the vein of Dr. Mario, but with a slight twist - instead of simply clearing tiles from the screen, you're given objectives to fulfill - survive a set number of tiles, get a set number of Klaxes or diagonal Klaxes, earn a certain number of points, and so on. All while trying to manage space on a small 5x5 playing field and maintaining a stack of up to five tiles on your paddle; drop three or fill up the field without a match, and your game is over. It starts out simple enough, but staying alive quickly becomes a challenge. Better get good at matching up those diagonal Klaxes and setting up combos!
41. Balloon Fight (Nintendo, 1986)
It's Joust mixed with Joust and a dash of Joust on top. Well, okay, it's not a complete copy of Williams' classic arcade game; the hit detection is a bit more specific this time, requiring you to actually contact an opponent's balloons to break them rather than simply be a few pixels above them when you collide. There are also hazards like lightning, spinning bumpers and giant fish trying to eat you to impede your progress. There's also a new gameplay mode, "Balloon Trip", where the object is to make it as far as you can before you hit an electrified bumper or get eaten by a fish. It's one of the better early NES games and among the first to feature two player simultaneous play as well. So derivative it may be, but it's also quite a lot of fun.