The main platformer Mario games are all pretty solid, if anything Mario Party is the only one that's not been great. Metroid has nothing but good games save for Other M, which was developed by the guys who make Dead Or Alive, so it's not like anyone should have expected much.
Sonic doesn't need to die so much as stop adding all that weird storyline shit (were-hog, knights, etc) with extra fluff characters. Sonic Generations is the first great game in awhile, though I've heard Colors isn't bad.
Final Fantasy needs a reboot, not a cancellation. They need to look at solid titles like the Tales Of games to see how a more modern JRPG can still be outstanding without turning into Final Hallway XIII.
The only series I'd like to see stop for awhile is the wartime FPS stuff. Not so much for the style of game, but for the way they've changed gaming and the culture surrounding it.