I've heard of the series being outrageously popular in Japan. They're slowly moving it over to America and other places now.
Also, Monster Hunter Tri is coming out for the Wii very soon with online play. You can search up online play videos via YouTube. It looks pretty neat, but I think I'm going to wait and see how it does. I managed to bum the demo off from the guys at gamestop for free, and from what I've played it was decent, just empty seeing as it was like a random slice of the game.