by the end of the gen, the 360 will tap out around 50 million while the ps3 will make it at least to 75 and not fall too far short of the wii. ps3 will be closer to wii in the end than psp to ds.

Success needs to be measured against the manufacturer's goals. Did they achieve what they set out to achieve?

 No. It's only one factor and not the biggest one.

Would you honestly think Xbox was more successful than the PS2, just because you were told that MS had a goal of selling say 15 million units?

For me, success is only achieved when goals are achieved.

Sony set out with the goal of dominating the industry once again, with the PS3, and they failed badly.

Nintendo achieved their goals, and then a bit more.

And I don't really know about Microsoft, though I suspect they didn't sell as many consoles in their first year alone on the market as they would have liked, but I would still categorize the 360 as an overall success, however small or large it may be.

^ IMO This.

Also, there will always be some people who enjoy a failed console (Amiga CD32), so I would say that sales/profits is the only indicator of the amount of people being entertained at home AKA Success.

Profit

even it failed to make the money that Sega must have wanted it to since they retired it, the dreamcast is considered to be one of the most successful consoles ever due to the strength, innovativeness, a quality that the 360 has very little of since almost all of the AAA games in its library are all from one genre, and the aspirations of its game library. So money can't be used as a measure of a system's quality. The Dreamcast is the second most successful console of this gen only topped by PS2. As IGN said in a recent article, "We failed, Sega." The DC never failed, and revenue plays no part in this fact.

Profits, expectations and competition.

The individual perceiving success for providing them with entertainment doesn't factor.  You can enjoy the console without it being successful.

Ah yes...lets not forget crystal ball success 'would-be prophet' BTFeather.

If someone sets out to achieve a goal and succeeds then I would say they where successful. Of course succeeding at a trivial goal carries very little merrit. There isn't alot of middle ground in public perception, that which does not succeed has failed. Was the xbox a failure? could it have done better?

Quit dodging.

If I set a goal to run 100 meters under 13 seconds, and I manage to do it, I'm more successful than Usain Bolt if he fails to set a new world record in the next Olympics?