Dynamite Cop. Okay.

I bought a ton of Sega games last gen, but the majority were just filler. Jet Set Radio, Seaman, even Beach Spikers and Sonic Adventure = Classic. Zombie Revenge, Dynamite Cop, Sonic Riders, and a ton more = crap.

Anyone with an asshole can release a ton of crap. I want quality. Capcom, Sony, Bungie, Nintendo, and Konami brought it WITHOUT supporting a dying (but still awesome) system. Sega HAD to bring the quantity.

I think the real test should be who brought the greatest selection of quality original IPs. Either new franchises or old franchises moved in a completely different direction. so, by that, many nintendo (shineshine, melee, etc) and sega (virtua figher, panzoor dragoon orta, etc) titles get the axe.

(also, some of the games in the original post were not developed by sega or a sega sub divison, just published). 

sonic adventure, crazy taxi, seaman, chu chu rocket, phantasy star online, skies of arcadia, jet grind radio, super monkey ball, ooga booga, nfl 2k, nba 2k, sega soccer slam, virtua tennis, metropolis street racer, nhl 2k

vs.

Nintendo was the best publisher of every generation it was involved with. I am not sure how many of the GC games it published were also developed by Nintendo. Let's not forget how some of Nintendo's GC games were let downs. Super Mario Sunshine and Double Dash were real letdowns for me. I was not huge into the last generation (I played maybe 35 total games) so I'll let yall argue about this but it just seems like Nintendo might not have been the best developer.

I think Nintendo is tops in this generation, though :)

nintendo
Capcom
two of the best game developers ever sega is a joke.

Hard to say who it would be, but here are the games that I would put as the top in each genre in the last generation

Fighting: Soul Calibur, possibly SSBM

FPS: Half-Life 2 PC

Action: GTA3 or RE4

Adventure:eh, tough to say. Can't think of many

Racing: GT5

MMO: Obviously WOW *raises flameshield*

RPG: FFX by far, ES4 comes close, but it lacks the substance that FFX has.

Ubisoft, Nintendo, Bungie, and Capcom.

Ubisoft: The entire Splinter Cell series
Nintendo: I hope I need not say anything here
Capcom: RE4
Bungie: Halo 1

Ubisoft brought Prince of Persia and Beyond Good and Evil too. Man, I loved those guys!!

To be fair, the GC and Xbox only sold about double the Dreamcast's sales when they were out 5 and 4 times longer, respectively.  But yes, I agree.

What I'm going for is that SEGA managed to make as much quality as these other developers while spanning across so many genres. Here's why SEGA and not others:

EA: Great at sports games, racing games, Sims games and....yeah not much else. Considering that 2K Sports was neck and neck with them throughout the 6th generation regarding review scores and considering that most people still bitch that they want Madden out and want NFL 2K series back in, i'd say Sega wins sports. As far as racing, it's a toss up between Sega GT and Crazy taxi vs. Need for Speed and Burnout. It's pretty much a draw with it going either way, but i'll give it to EA because Burnout is godly on review scores and godly in my heart. Sims games were gimped for their console releases while a game like Phantasy Star Online, Alien Front Online, Bomber Man Online and many others all featured good online support. Now how many other genres can EA compete in? Action-Adventure? Action? Rhythm? Puzzle? Yeah not much else. I can still name many more great SEGA titles across many genres that EA doesn't even develop in. No contest.

Nintendo: I will give props where they're due. Nintendo makes great games. They just don't make enough of them. Let's start at the top...racing. Nintendo has a few like Mario Kart Double Dash, Mario kart Super Circuit which was great and F-Zero GX which was (gasp) made by SEGA. How about racing games that aren't kart based? Nintendo doesn't make them. SEGA makes plenty of racers of quality in both arcade and sim style. Star Fox Assault vs. Panzer Dragoon Orta? No contest. I will give Nintendo their due that Wind Waker and Twilight Princess trump the Shenmue duo. I'll give an even match of Sonic Adventure 1-2 up against Mario Sunshine and Luigi's Mansion. Virtua Fighter 4 vs. Super Smash Bros. Melee is an even match. Metroid Prime 1-2 is a given for Nintendo, since SEGA has nothing to compete against it with. Nintendo also spent most of the 6th generation retreading old franchises while SEGA created mounds of new original IPs. What happens though is that Nintendo loses out because they are about quality over quantity and SEGA was about quality + quantity. I would rather have those extra choices.

Bungie: Please don't joke around. They aren't even comparable because of size alone. They have Halo, Halo 2 and Oni. That's two awesome FPSes and a mediocre action title. Wow! Where's the support for the other 20-something genres out there? 

Insomniac: They made four games all generation and each one started with the word Ratchet. The highest metascore for a Ratchet and Clank game was the 91 for Up Your Arsenal. SEGA has about 20-30 game that scored higher than that and probably another 40 or 50 in the 80s. Considering the each Ratchet is just one series in one genre, Insomniacdoesn't have anything to show for quite a few other genres out there. Not only are they small, but they spent 4-5 years milking one franchise without doing anything else.

Rockstar: The three GTA's are masterpieces. Midnight Club Racing, Bully and Max Payne are all borderline A status games. The Warriors, Max Payne 2, Smuggler's Run and Manhunt were great games. State of Emergency, Manhunt 2 and Red Dead Revolver were good games. Spy Hunter 2 was garbage. That's a great little lineup but it can no break into how many great games across so many genres that SEGA's lineup has accomplished. I will say however that if Rockstar was as big as SEGA was, it might have been very hefty competition.

Capcom: I knew this would come up. This is the ONLY other developer/publisher worthy of the prize and I can see a convincing argument for why they deserve it. Capcom has strengths in fighting, action and action-adventure where SEGA has strengths in sports, racing, and action. I'll come back later with both up against each other with gamerankings. I can however see the argument made for Capcom. 

Fixed

PD: GT5 is not launched yet.