In my opinion it started when sega decided to make the piece of crap 32x and the piece of crap sega cd.  This was then followed up by another piece of crap.  So by the time their next item was released everybody just assumed that it was crap.

Genesis(1988) came out 2 years before SNES(1990). That, aggressive marketing, Sonic, and EA Sports helped Genesis out. But, the real fact was that Genesis was actually competing well against NES, not SNES. Once SNES rolled out Sega tried to stop the quick drop in marketshare by releasing expensive and hardly supported addons, SegaCD and 32X. However, as I discussed above, these actually hurt Sega in the long run.

It would have been better had sega not released either of the addons and put out the Saturn when it did and then followed that with the Dreamcast at a much more reasonable timeframe.

Sega did compete decently against the SNES in America for a short time. This happened when Mortal Kombat blew up.

This is because there is no data available for US game sales in that time frame. Sega sold nothing in Japan... Otherwise there would be lots more genesis games in the million seller list. Do you really think Eternal champions, Streets of rage 2, nhl 94 sold nothing...all those games sold atleast 2-3 million on the genny.

@superchunk

Genesis was targeted at nintendo first but failed. Only in 1992 did genesis take off in the states. Snes saw very little marketshare in the States until 1994 when donkey kong and super metroid came out.

I'm just saying that the likes of Shinobi 3, Golden axe and Streets of rage 2, sonic and phantasy star 2,3 and 4, Vectorman, ecco the dolphin and sega sports titles like the best baseball game (world series baseball) along with EA and midway's efforts...Sega could easily compete with the Snes and actually had the lead for the first 4 years of super nintendo's time frame(in US).

The only reason genesis lost to Snes in the united states is because Sega abandoned it in 1996 completely to focus on the saturn and stopped making it while Snes was made well in to 1998. In 1995 it was still the leading 16 bit console total sales wise...

As far as those 32x, sega cd addons...this was the sega's constant need to be technologically better than the competition and to try to reinvent the wheel. If they had just focused on making games like usual and not bothering with hardware and released the Saturn like you say(which was technically better than PS1), they may still be around as a hardware manufacturer.

I disagree with your timeline/sales, but I cannot find good sources so....

Originally I stated that Sega did not have the ability to hold its own like Nintendo off of its own IP's. You disagreed, yet you give a list of a mixture of Sega and 3rd party games. I would bet that you could take the total sales of all Sonic's main games ever created and that total would be less than Mario+Zelda+Metroid on one Gamecube, Nintendo's most unsuccessfull system, which sold more than Saturn + Dreamcast.

Plus, I have already been proven true, Sega couldn't live on their own with the Saturn or Dreacast. Yet, Nintendo did it very profitably with both the N64 and Gamecube.

This isn't really a slam against Sega, in reality there does not exist a game publisher that could live off its own software like Nintendo can. 

Actually I found a good source.

http://vgchartz.com/worldcons.php?date=34029&sort=1

Our shipment tables show that by March 1993 SNES had already shipped 6m+ more units than Genesis did. It is obvious that in less than 3 years SNES already had outsold Genesis, even in the NA market alone.

Genesis was doing well against a much weaker system, NES, but, always lost vs the SNES.

http://vgchartz.com/worldcons.php?date=34759&sort=0

The last chart available before saturns launch...

Genesis and Snes are neck and neck with Genesis outselling the snes in the states for the timeframe by more than 5 to 1.

I wasn't arguing that Sega could compete with Saturn and Dreamcast games. Something changed in Sega around the 1995 timeframe and Japan took control of the company. Sega's heart was always the Amercian side of the company...
Snes had huge 3rd party support as well...as good if not better than genesis. (Konami, Capcom, Square...) Where genesis was getting low key developers like treasure to make amazing yet unknown games... So don't tell me that Sega softtware couldn't compete with Nintendo software in the 16 bit generation. If nintendo didn't have Square support alone they would have lost to Genesis.

You pulled out the only chart in existance where Genesis beat SNES. Good job.

Obviously something major happened during that 6 months. Some major game, residual hype from Saturn launch, massive price reduction to clear out stock (likely), idk. But, to use an obvious exception as the rule is just wrong. Up until that point SNES had a multimillion unit lead in NA. The only place Genesis ever beat SNES regularly was "Others" due to sport titles since Nintendo received no support in that form.

To me it seems they are neck and neck...snes has the lead of 600K units at that point with Genesis having the momentum.

14.74 vs 15.39

But lets see...Saturn comes out in next quarter...Snes sells 1.27 vs 0.74 for genesis.

Sega officially drops support for Genesis next quarter...Snes sells 2.10 vs 0.83

What happens when n64 comes out next quarter...aww snes sells 0.64. This is what happens when a new system gets released.

In any case, Snes still supported super nintendo until 1999.

Sega stopped making genesis systems and games before christmas 1996.

The stroke of genius of SoA with Genny was that they understood that children grown with Nes were ,at the time of genny release, teenagers.

So they reached an underserved ( by Nintendo ) market, plus they had 2 years advantage respect Snes US launch.

The other problem of Nintendo at that time was its iron-fist releationship with third-parties. I think third-parties hoped at that time that Sega would save them from Nintendo greediness.

The problem was that Sega was just like Nintendo, they wanted to be the next Nintendo.

Sega only purpose was to defeat Nintendo ( and viceversa ) and in doing this both company damaged themselves.

Sega, unlikely Nintendo with Nes, hadn't had the time to build a safety cash reserve and they lost money on unsuccessful add-on ( for the sake of competition ).

Sega Saturn was a powerful console but was difficult to code, was to focus on 2D when 3D was the next big thing, was too expensive ( 400$ vs 300$ , only Sony at that time sold console undercost ...), in first couple of year Saturn's development kit were in assembly ( language machine ) when those for PS1 were in C.

Nakayama stopped support for Genny in 1996 because they needed all company resource to promote Saturn against Sony's PS1 ( they didn't have the resource of Sony or Nintendo ).

Sega does what Nintendon't: Nintendo was always profitable.