hmm, given I had all three consoles....
I would say 360 for GTA4, and then Wii for MKWii, and then PS3 for an exclusive.
I really wish GTA4 was coming for Wii. So far there have been only two games I wish I had a 360 for. GeoW and GTA4. PS3 still doesn't have anything exclusive that I really miss. Maybe MGS when it comes out.