I based the most important companies on how much they contribute to the awesome content of the generation. Sega, whether you like them or not, still pops out amazing games. Last generation we saw Panzer Dragoon Orta, Shinobi, 2k sports games, PSO, Jet Set Radio Future. This generation..my gut just says Nights 2 will be great. Sonic is not beyond restoration...and I think they can come up with some new IP. Capcom has been awesome lately - Resident Evil 4 is pretty much the best game of the last generation. Okami, Viewtiful Joe, Monster Hunter, Megaman, Street Fighter, 1942, Red Dead Revolver (the wildwest game..am i thinking of the right game?), Resident Evil, are all among the best games I have ever played in their respective eras as new IP. I sincerely doubt Capcom won't come up with new IP this generation. Consider also that it is Capcom that is helping Microsoft above just about any Japanese (Lost Planet) in winning the West...Keep in mind too that as a publisher, Capcom introduced GTA pretty well into Japan. As for THQ, Activision, Namco-Bandai...they all produce regional, and specific console hits...but they are not really pushing the boundaries. THQ lives off its liscences (like the WWE games) which fund more expensive games that are new IP. Namco is trying to become a western game maker...but I would say the direction isn't working real well so far. Bandai is partially owned by Nintendo and Namco...so I didn't include it in consideration. Activision is good for producing mass-market games, but it isn't the kind of company that forces the industry forward with real innovative games (look at Guitar Hero...the design is pretty similar to DDR, except you strum instead of moving your feet)

1985-1988 - "Nintendo the Monopoly" Nintendo, Midway, Acclaim, Maxis, Sega, Namco, Square, Enix, Konami, Capcom AKA The Dark Ages!

Dark Ages? Only for Atari.. I mean this is the era of... Mario, Phantasy Star, Metroid, Ninja Gaiden, a plethora of sports and shooting games, the emergence of RPGS like FF, DQ, Zelda, Star Tropics... This is also the emergence of...Metal Gear, 1942, Street Fighter (may have been 89' I forget), side scroller beat 'em ups, Double Dragon, Megaman, Castlevania, Rystar, up-down-left-right... (not typing that secret all out) and so many others. The NES probably had around 1500 games...100-150 or so were great games...50+ of which hold up even today (Mario 1-3, Zelda, Metroid, Kid Icarus, Punch Out, FF, DQ, RBI Baseball, 1942, Megaman, Jeopordy, Double Dare, Kirby, Duck Hunt, Rystar, Ninja Gaiden, Metal Gear are some of my favorites...need I go on?)

While the issue of whether quality correlates to sales is its own debate, at some point, the companies that get that big generally do contribute positively to the gaming industry, even if they do also often flood the market with crap as well. My biggest problem with Sega and Capcom is unrelated to that, though. I just think they're stupid. One bad business decision after another. I don't think Nintendo's 1% ownership of Namco Bandai has much impact, certainly not more than Sony's 9% stake in Square Enix. I would suggest that the NES era was probably the darkest era of the lot, but there was a lot of classics as well. I'd take Sony's monopoly over Nintendo's, though it's apparent with PS3 Sony is becoming just another Nintendo.

Sony has never had a monopoly though. Worldwide, it peaked at around 75% marketshare. In 1988, Nintendo peaked at like 93% market share. Sony was dominant, but to me, 90%+ is a monopoly.