I would consider the PS3 a success since it already achieved a core goal, winning the format war. I think if it is able to become profitable it will become a complete success.
The Wii is obviously a success for many reasons.
The 360 will be a success if they manage to increase their market share from last gen and also turn a profit.
edit for grammer
Currently Playing: Saints Row 2 | Battlefield 2 | Company of Heroes
Recently Beaten: Gears of War | Super Mario Galaxy | Darwinia | MGS4 | Sam and Max Ep. 4, Portal | Mirror's Edge | Uncharted | Mass Effect
Looking Forward to: Alan Wake | Splinter Cell : Conviction | The Last Guardian | Batman: Arkham Asylum | SMG2 | Mass Effect 2 |