Spiegel said:
MHG had a demo of MHTri and MHP3 has sold 4.5M already.
I don't think the demo means much, and the PSP already had a port of G at the time too, as well as a port of its sequel by then, with the success they had.
Oh, and the second game's expansion was already out too, for like 1-2 years or something.
Monster Hunter Portable is a port of G, Monster Hunter Portable 2nd is a port of Monster Hunter 2, Monster Hunter Portable 2nd G is that game much expanded.
Portable 3rd likely has more differences than 2nd does against 2nd G, it's a different and the latest game.
So, yes, G was very much outdated and outclassed at the time by 3 newer iterations (including its enhanced port to the PSP) while 3rd isn't.
Monster Hunter G on Wii also has fees for the online mode (I think it's still running, though they shut down the PS2 servers).