The PESRankings Winner and the winner of the End of season Grand finals gets invited to the World Finals. The_Greek won both Rankings and the Grand finals this season got to go and Footimaster who came 2nd in Pesrankings got to go because The_Greek won both places and obviously has to let someone else go.
During the season you can play on the format you desire. Be it Ps3, xbox360, Wii or Pc. Theres is one big ladder thats involves everyone. So you can play Wii the whole year and finish 20th and you would qualify for the Grand Finals at the end of the year. Usually these big events are held on Xbox360's. They may change in the future, who knows?
But only if you win Pesrankings or win the Pesrankings Grand Final at the end of the season allows you to take part in the Pes World Finals
Hopefully you understand what i've written