Probably Little Big Planet 2. It's HD and you can do much more than just 2d platforming.
As far as the two Nintendo ones go, I don't think either one will have the sales of New Super Mario Wii and in the end they will cannabalize each other's sales. They should have gone with one 2d and one 3d platformer (preferably the DK game as the 3d one since Retro is suppossed to be on the cutting edge as far as Nintendo studios go).
I went back and watched the Sonic and Rayman games. Sonic looks good if you like old school Sonic and it's a wiiware game which is a plus as you won't have to pay full retail game price for it while purchasing both Kirby and DKCR could run you close to $100 for 2d platformers in 2010.
Rayman Origins looks really good. I think it is more mature and creative than what we've seen from the others, so I would put it up there at the top for what should be done with 2d platforming in 2010.
Also this: http://www.youtube.com/watch?v=w_a6JpUIu84
and this: http://www.youtube.com/watch?v=9l35FJr-nqM
And the XBLA game Limbo ( http://www.youtube.com/watch?v=EGgtnyXfVv4 ) is supposed to be good.
So, I would say 1. Blade Kitten (PSN) 2. Rayman Origins 3. Limbo (XBLA) 4. Little Big Planet 2 5. Kirby's Epic Yarn
