Zelda, Super Paper Mario, and Mario Party are all great but a lot say they are slightly under par for each for their series. Rushing more games won't help.
I think they have been working on SSBB for a little longer than you think, the continued push back of the release date indicates they have no intention of rushing this one through quickly. Also who thought Zelda was under par?
Mario Kart is a classic, started on the SNES. I'd be surprised if they don't continue the sucsessful franchise on the Wii. I think they should add more characters, online play and no Double-Dash format. That rumor is good.
Perhaps the reason why games like Mario Party 8 are so shitty is because they have a lot of their resources focused elsewhere.
I meen all Nintendo games out right now, Zelda and Super Paper Mario arn't shitty but look at the mass opinion and it'll be lower on these games then the previous ones. Not by much, neither were failures or anything but they are just a little under par from what should be expected.
I can dig up some statistics of review scores (both user and profesional) compared to release dates
And if they weren't rushing the cycle they'd have time (or resources) to make all of thier games high-quality. Mario Party 1 didn't suck and yet the Mario and Zelda of the time are often considered the best in the series.
I'm just being general here though. As a whole if you compare the Nintendo line-up at this point in the systems life-span compared to where they were at with the other systems it just seems like it's going by much quicker and suffering because of that.