We have the very first candidate for being game of the year 2010, its called VVVVVV (yes thats 6x V) :P

Trailers
http://www.gametrailers.com/video/topsy-turvy-vvvvvv/60768
http://www.youtube.com/watch?v=sf06P-_1lkU

Online demo version in flash
http://www.silvergames.com/game/vvvvvv/
http://www.kongregate.com/games/TerryCavanagh/vvvvvv-demo

It is a hardcore platformer, that requires fast thinking and even faster reacting. It has a good tempo, and great soundtrack that fits in perfectly. If you miss the times when you could actualy brag about beating video game, and there was no such thing as difficulty settings, then it is a game for you.

You can buy whole game (35MB) for 15 bucks on http://thelettervsixtim.es/
It isnt long, I finished it in 2h 11m 33s with 19 out of 20 trinkets (bonus items), and 2h 30m 15s with all 20 (missed Im Sorry/Please Forgive Me one), but intensity and fun factor makes it worth.