Based on: Astro Boy, silly musical puns, elemental weapons and levels, and time-honored 2D platforming.
As a series, Mega Man has great music.
This might not be the most intuitive starting point for discussing the maiden voyage of Mega Man, the widely-played and well-recognized Blue Bomber of gaming lore. In Japan, however, the music angle is more pertinent, since their Blue Bomber is actually named Rockman. As the story goes, 200X was the year in which one Dr. Thomas Light came to create a wonderful new peace-keeping robot to provide company for his Roomba vacuum cleaner. This robot's name was Rock.
Dr. Light was a young soul, you see -- even at age sixty, he was very open minded about music, with a fondness for old B.B. King records and, more recently, Radiohead's album OK Computer, which by 200X was a rock classic. He went on to create Roll, a robotic maid which ended up replacing his aging Roomba, and later a musical robot with fondness for whistles and mouth harps named Blues.
At the time of the first Mega Man, however, Dr. Light had only Rock and Roll to call his own. And this fits, because really this first Mega Man game is much more Pablo Honey than OK Computer. It's a music that's raw and sort of squirrelly, and like that first Radiohead album no-one would predict that future entries in the line would become a torch-bearing standard for the genre.
For its time the game was innovative, although not in a way that other titles would immediately start copying. Six stages were selectable in any order from the start of the game, each with a unique theme and Robot Master at the end. Some of the stages were interesting and fun, while others were just drab and a couple were exercises in disappearing platforms that would just totally piss you off.
But the similarities to Pablo Honey continue. Just as that album has an easily-overlooked depth and quality to its production, Mega Man had very balanced gameplay that drew from the ability to acquire special weapons from a defeated Robot Master. First of all, these abilities kicked ass in an objective sense. Whether you chose to hurl giant bricks, turn up the heat with a combination fire shield/flamethrower, or brandish lightning to cut wide multi-directional swaths of ownage, Mega Man allowed an extremely satisfying latitude to how you ruled over minor enemies.
Any player quickly learns that special weapons provide a necessary advantage against a difficult Robot Master -- Ice Slasher against Fire Man, bombs against Guts Man, etc. -- which is in itself pretty clever. But what most players don't see is that many facets of the stages lend themselves to particular weapons. Enemies are often arranged in ways that a clever player can exploit with the proper weapon, and once you discover these little strategies, Mega Man becomes a truly fun little platformer.
After beating all six Robot Masters, the fun-loving Dr. Wily invites you to his beautiful techno-gothic vacation resort to relax, sunbathe, enjoy tea and crumpets, and be viciously murdered by gargantuan horrors or -- more likely -- spikes. Like any mad scientist, Wily doesn't find it appropriate to simply construct a huge fortress covered by impassible spikes and surrounded by bottomless pits -- rather, he leaves the tiniest safe path such as to tempt our hero into penetrating his fortress and dying in the process.
At this point, clever application of Mega Man's special weapons is no longer optional. The first Mega Man game is particularly difficult, but often explicit in placing enemies in a way that a single vertically-oriented Thunder Beam, well-placed Rolling Cutter, or perfectly-timed Fire Storm will save the day. The suspense kicks up, and suddenly all that added firepower seems perfectly fair, with more and more enemies placed in just the spot that will cause you grief and humiliation.
Without the later innovation of energy-restoring E-Tanks, Wily's castle is a battle of skill and strategy, as you carefully ration your life energy and weapons energy according to the challenges ahead. Yes, there is trial and error, and you will die multiple times. But once you've figured out the best strategy to defeat four Robot Masters in a row without dying, and determine the optimal weapons for each of Dr. Wily's final boss forms, you'll feel a tinge of pride.
The original Mega Man game is bastard-hard, and as an early-generation NES game certainly looks its age, but perhaps those players in 1987 who pushed on through to the end might have glimpsed the remote possibility that Capcom had the beginnings of a truly exceptional game. For everyone else who appreciates solid 2D platforming, you could do much worse than give Mega Man a try.
Besides, the game's got some really catchy tunes.