The three official steps to success...
1) Games
2) Killer app games
3) More games
Lets be honest here, it's the games that will decide the competition next-generation. Just like the PlayStation 2 didn't really take off in sales until the release of Grand Theft Auto, and Halo alone managed to sell Xboxs, or Goldeneye 007 brought the Nintendo 64 its success, and Pokemon got a Game Boy in every child's hands...it will be the killer apps - those special, rare titles of which we only see maybe two every generation - that will be the deciding factor of who will be the top competitors.
It's part luck...and part ambition. But my prediction, is that Nintendo consoles - the Revolution and Nintendo DS - have the best chance of receiving the next killer app courtesy of all the new features being integrated into them. Developers will have more options when creating their games.
With the NES, we received 2D games and the killer apps that went along with it. With Genesis and SNES, we nearly perfected 2D and received those games that came along with it. With PlayStation and N64 we were introduced to 3D games. And now with Xbox, PS2, and GCN, we've nearly perfected 3D. Next generation, it's going to take something more than just more expansive worlds and pretty graphics to incite a new gaming phenomenon.
Will it be an online game? Yes, that's possible. But remember, Nintendo will have that and more.