Every New Super Mario Bros. has sold very well. Some better than others for obvious reasons.

However, Nintendo seems to develop only one game of the franchise for each console (with the exception of the NSLU DLC).

The development costs shouldn't be too high either. People obviously want more Mario games, so this might help to shut those people up (probably not though).

The quality might be lacking over the years, but just from a sales perspective, NSMB should be an annual franchise.

I say bi yearly.

HELL NAW!! I don't think ANY FRANCHISE (other than sports games) should be an annual franchise. This is why COD is getting old too quick...

You see that decline thing going on there?

Not so sure that's a good idea. The Mario brand is already dying but Miyamoto is convinced it's Nintendo's Micky.

Please no...

No, but I see a smaller install base being a reason for that.

I would say yes if the games were appropriately-priced. A new level pack (because that's essentially all the 2D games are) for $20 each year would be fine.

Yuck.