Defining each companies "prime" might be good too. I'd say Nintendo and Sega have each had two...
Sega 1st (1987-1992: System 16/24/32 & MD/Genesis era)
-Constant string of arcade super-scaler hits (Outrun, Afterburner, Power Drift, Galaxy Force, etc). Helps drive the early push for 3D gaming.
-Genesis brings arcade hits home in recognizable translations for the first time (Altered Beast, Shinobi, etc).
-Sega massively expands consumer R&D for Genesis. Franchises like Sonic, Streets of Rage, Phantasy Star and others are born.
-Sega actively scouts for conusmer talent, funds tons of start ups (Climax, Ancient, Treasure, Camelot, etc).
-Makes key deals with Capcom and Falcom for Sega developed arcade/PC ports. Signs Namco as first Japanese MD 3rd party.
-Sega Sports (along with EA Sports) actively expand the console market.
-Successfully breaks Nintendo's stranglehold over the industry. Edgy advertsing and sports focus paves the way for today's casual gamer (ie: PlayStation).
Sega 2nd (1994-1998: Model 1/2/3 & Saturn era)
-Model 1 3D games wow arcade goers. VF & VR set the standard for future 3D fighters and racers.
-Model games cement Sega's position as the 3D leader, with genre-refining releases like VF2, Daytona USA & Sega Rally. Sega's at it's peak quality wise imo.
-Saturn shows the superior abilities of Sega's game R&D teams. "Impossible" conversions of VF2, Sega Rally, Virtual On and others become the norm.
-Consumer R&D hits it's creative height imo. Properties like NiGHTS, Burning Rangers, Dragon Force, Sakura Taisen, Panzer Dragoon and others show Sega at their best ever in the home.
-Japanese 3rd party support ramps up in the face of western decline. Top support from Capcom, SNK, GameArts, Atlus and others make Saturn become the ultimate import machine.
-Sega starts investing heavily in online/network R&D. As always, ahead of their time.
-Model 3 shows first glimpse at what the next generation holds.
Nintendo 1st (1985-1990: NES & GB era)
-Famciom becomes a significant moneymaker and NES takes the rest of the world by storm. The platform rebuilds the videogame from the ground up, defines the structure of the closed platform console market and to this day remains the most dominant console in history.
-Super Mario Bros revolutionizes game design. Games shift from arcade style "score based" to console style "progression based" design in the face of it's massive success.
-Nintendo pushes console gaming with "battery saving" in expansive, explorative games like Legend of Zelda and Metroid. Moves out of arcades entirely and forms dedicated superstar EAD division.
-Experiments with rewritable media and optical media. Nintendo also begins experimenting with networks and online infastructure.
-Super Mario Bros 3 becomes a phenomenon. Successful media tie ins (with the film the Wizard and McDonalds toys) chart a blueprint for the future of cross media interplay.
-Game Boy hits the scene. Nintendo successfully creates a secondary, complimentary handheld games market.
-Nintendo secures game rights to Tetris, arguably the most popular game in history. Tetris in turn drives the casual Game Boy market.
Nintendo 2nd (1996-1999: N64 era & GB revival)
-Nintendo 64 releases. Console gaming shifts focus almost entirely to 3D.
-Nintendo makes multiple controller innovations with analog input, a finger trigger, camera buttons and expansions like the Rumble Pak, Memory Pak and GB Pak.
-Super Mario 64 drives N64 critically and commercially. EAD releases critical/commercial N64 hit after hit (Wave Race 64, Star Fox 64, 1080, Ocarina of Time, etc). They set the standard for 3D game design throughout the industry.
-Nintendo solidifies relationship with Rare through investment and co-op R&D. Branches out into other western 2nd party relationships and funds multiple JP start-ups.
-Goldeneye becomes a surprise hit through positive press and word of mouth. Helps establish multiplayer gaming as key focus for Nintendo.
-Pokemon single handedly revives the dead Game Boy market. Goes on to become the fastest growing game franchise in history and becomes the model for media tie ins and merchandising. Brings in another young generation of Nintendo fans and forms todays kid-focused, social minded handheld market.
...what's everyone else think? Agree/disagree?