I have to agree about Yoshi's Story. I mean, it's not a HORRIBLE game, but it's just a big step down from the brilliant Yoshi's Island, and every other previous Mario-related side-scroller. It seems as if Nintendo decided that side-scrolling games should just be for kids and weren't as high a priority as big 3-D games. YS has beautiful graphics and the Yoshi voices are cool (except when they sing), but the gameplay is just TOO easy and one-dimensional, the music is rather cheesy and repetitive compared to NES and SNES Mario games, and the whole game just reeks of cutesiness. I can only hope that with the success of the Super Mario Advance series and other side-scroller ports like Donkey Kong Country and Nightmare In Dreamland (aka Kirby's Adventure), that Nintendo will have learned their lesson and will once again set out to make a great side scroller.
Oh and as for the Mario Party series, I think that Mario Party 3 and 5 are totally unneccesary sequels, and MP2 was only neccessary to get rid of those spin-the-joystick games.