If I had to rate it would be:
1> NES. This was the foundation for a LOT of huge franchises, not just Nintendo franchises as well. Plenty of fun games, some still hold up in how challenging they are today.
2> PS2. Plenty of awesome exclusive 3rd party titles, and was backwards compatible so it included all PS1 titles
I can't rate the Xbox 360 and PS3, they have only a super-limited selection of exclusives, and beyond those limited exclusives, they're basically the same with different online connections.