Sega
Sonic The Hedgehog

"Genesis does what Nintendon't"

This phrase, as boastful as it is ungrammatical, was the beginning of the most epic of console wars. It was certainly not the first, but compared to it, the skirmishes of the early '80s between Atari 2600 and Mattel Intellivision were childish pranks that were silenced in 1983 by the Great Video Game Crash, an event never sufficiently remembered in the annals: the market became saturated, consumers grew tired of a choice so vast of still embryonic and mostly unreliable technologies, and consequently many companies failed.
...silence...
Then, a new bang, in caps lock: NINTENDO ENTERTAINMENT SYSTEM. It was 1985, the Renaissance, a miracle brought forth by a Japanese company that previously made playing cards and managed to sell 60 million NES consoles (Famicom in Japan) and establish a solid monopoly with the help of an Italian plumber (former carpenter) and some not particularly honest exclusive contracts.
The other manufacturers who once thrived could only watch and plan a grand comeback. Like Atari, which after the success of its 2600 and the huge flop of the 5600 tried to get back on track with the good but not exceptional 7800, then moved from numerology to felines with the Jaguar and the portable Lynx, which definitively knocked it out.

Another much older company (1951), SEGA, whose roots were in the photo booth machine business, wanted to try to break into the revived 8-bit console market with its SG-1000 Mark III known in the West as the Sega Master System. It mattered little that it had better graphics than the NES and some charming accessories like glasses to see games in 3D; the lack of flagship games could not compete with Nintendo’s incredible catalog full of instant classics.
Even though the Master System was far from obsolete (not surprisingly it was much more successful in Europe, and I received a version II as a gift in 1994) Sega made the first move and introduced the fourth generation of consoles already in 1989 with Genesis, known in Europe as Mega Drive (and advertised in Italy by Gerry Calà with Sega pronounced as "Siga" to avoid unfortunate ironies).
"Genesis does what Nintendon't," and while on one hand it was an insolence well justified by its 16-bit power, on the other Sega continued to suffer from a game selection that was not really stellar (a game with Michael Jackson... seriously?) and was sold in a bundle with what was considered its killer application, Altered Beast, a game technically advanced for the time (ooooh, listen to the voices: "Welcome to your doom!". Scary!), although it aged quite poorly and generally offered nothing gameplay-wise that hadn’t already been seen in 8-bit. There was nothing to be done: a symbol was needed, a mascot that could poke the fat plumber in the behind.

And in 1991 that symbol came rolling down a green hill at 200 km/h, was blue, and was super cool, arriving at the photo finish a couple of months before the arrival of the Super Nintendo Entertainment System, Nintendo's 16-bit console. The Great Console War had truly begun, with an atomic explosion, indeed supersonic. That symbol was Sonic the blue hedgehog, one of those sprites, a heap of pixels, that can change the course of video game history if only given the right momentum.
And Sonic The Hedgehog had that momentum, a platform game very different from its Nintendo nemesis. If Super Mario Bros. focused everything on precise centimeter control of the character, Sonic leaned towards a more over-the-top approach where such control could even be lost in favor of the final goal: reach the end of the level as quickly as possible. Running at crazy speeds along descents, loop-de-loops, cliffs, breakable platforms, mowing down enemies and collecting gold rings (the equivalent of Mario’s coins) in abundance. Being careful not to be touched by enemies since, in that case, you must witness the painful scene of all the rings you carefully collected earlier scattering around. Painful also because Sonic dies if enemies touch him again when he has no rings and because you need at least 50 rings to access the bonus levels. These are psychedelic and gravity-free rotating pinball machines where Sonic spins and bounces to reach the Emeralds coveted by his enemy, the wicked Dr. Robotnik. Once the game is completed with all 6 Emeralds, we can enjoy the best ending of the game. Difficult but satisfying.

Levels structured both vertically and horizontally can be traversed in different ways depending on whether you seek pure speed or opt for a more exploratory approach, and every 3 levels Sonic faces Dr. Robotnik who, like a Japanese Wile E. Coyote, offers a new machine each time to try to end his spiky adversary's wild run. Defeating Robotnik, Sonic can move on to the next zone, themed differently from the previous one: Green Hill Zone, the first, is Sonic's trademark, showcasing its potential, colors everywhere, and steep descents; Marble Zone is “Pompeian” in its blend of lava and ancient architecture; Spring Yard Zone is a pinball machine with acid colors, neon, and repelling structures; Labyrinth Zone, a mysterious submerged temple, is the slowest and most dangerous as Sonic cannot stay underwater too long; finally, Star Light and Scrap Brain Zone are technology-themed (and perhaps the least inspired).
The visual aspect is the real driving force of the frenetic hedgehog: on screen, we can see all the colors of the rainbow simultaneously, the image is vibrant and seems to jump out of the screen despite being merely a two-dimensional game, thanks to the highly effective parallax scrolling backgrounds that move with the character. Nothing like this had been seen before, and even the more powerful Super Nintendo struggled to emulate this style. Furthermore, the bubbly and memorable techno-funk soundtrack by Masato Nakamura emphasizes this explosion of color.

So, if from a gameplay standpoint Sonic is a simple platformer, it's the small innovations and the perfect blend of elements that make it truly unique: a trip so lively that not even the mushrooms from the mustached character created by Shigeru Miyamoto can deliver.
Sonic The Hedgehog harkens back to a time when console wars made sense because they pushed truly different systems depending on the type of games they offered. It was the sought-after gaming experience that defined the best purchase: a subjective matter, not a hardware one.
As we well know, wars never have winners and lead to many bad decisions. Sega tried to close the technological gap with costly and unsuccessful add-ons for the Genesis: the Sega CD and 32x. Nintendo, during the design process of a CD add-on, refused a partnership with a major company. This company turned against it, developing the add-on as a standalone console: the Playstation. We know how it ended in the next generation.

Sega and Nintendo struggled in the next two generations of consoles with, respectively, Saturn and Dreamcast and Nintendo 64 and Gamecube. But Sega much more so, such that in 2001, in severe financial difficulties, it had to discontinue the Dreamcast, focus solely on software development and make a peace treaty with Nintendo.
Despite everything, Sonic The Hedgehog remains and will remain an epic video game that has wonderfully withstood the test of time. Today, it is possible to play it on any platform (including the Master System, in a reduced and different version but identical in spirit). It is found in various compilations or on the various download services like Xbox Live Arcade, Sony Network, Wii Virtual Console, etc. But even a simple emulator will suffice. In the end, while the sequels were good and even more action-packed, they failed to match the original's charm, and particularly the transition to 3D was not at all smooth, but today as yesterday, Sonic remains Sega’s cool mascot as Super Mario remains Nintendo’s.

And 20 years after their first showdown we can see them competing peacefully at the Olympics.